Correct the rule description (#1467)

### What's done:

 * Originally, the description of the `KDOC_CONTAINS_DATE_OR_AUTHOR` has had the
   reverse meaning. Now it's correct.

info/available-rules.md

@@ -41,7 +41,7 @@
 | 2    | 2.1.3    | KDOC_NO_NEWLINE_AFTER_SPECIAL_TAGS        | Check: warns if special tags `@apiNote`, `@implNote`, `@implSpec` don't have exactly one empty line after.<br>Fix: removes redundant lines or adds one.                                                                                                        | yes | no                                                                                                                                                                                                                         | Handle empty lines without a leading asterisk.                                                                                                                                                                                   |
 | 2    | 2.1.3    | KDOC_NO_DEPRECATED_TAG                    | Check: warns if `@deprecated` is used in KDoc.<br>Fix: adds `@Deprecated` annotation with a message; removes the tag.                                                                                                                                                | yes | no                                                                                                                                                                                                                         | The `replaceWith` field in the annotation can also be filled with a meaningful value.                                                                                                                                                                            |
 | 2    | 2.2.1    | KDOC_NO_EMPTY_TAGS                        | Check: warns if the KDoc tags have an empty content.                                                                                                                                                                                                                 | no  | no                                                                                                                                                                                                                         |                                                                                                                                                                                                                               |
-| 2    | 2.2.1    | KDOC_CONTAINS_DATE_OR_AUTHOR              | Check: warns if the KDoc header contains the `@author` tag.<br>Warns if the `@since` tag contains a version and not a date.                                                                                                                                                  | no  | no                                                                                                                                                                                                                         | Detect the author by other patterns (e.g. 'created by' etc.)                                                                                                                                                                      |
+| 2    | 2.2.1    | KDOC_CONTAINS_DATE_OR_AUTHOR              | Check: warns if the KDoc header contains the `@author` tag.<br>Also warns if the `@since` tag is present but contains anything but version (e.g.: a date).                                                                                                                   | no  | no                                                                                                                                                                                                                         | Detect the author by other patterns (e.g. 'created by' etc.)                                                                                                                                                                      |
 | 2    | 2.2.1    | HEADER_WRONG_FORMAT                       | Checks: warns if there is no newline after the KDoc header.<br>Fix: adds a newline                                                                                                                                                                                  | yes | no                                                                                                                                                                                                                         | Check if the header is on the very top of the file. It is hard to determine when it is not.                                                                                                                                             |
 | 2    | 2.2.1    | HEADER_MISSING_OR_WRONG_COPYRIGHT         | Checks: copyright exists on top of the file and is properly formatted (as a block comment).<br>Fix: adds copyright if it is missing and required.                                                                                                                  | yes | isCopyrightMandatory, copyrightText (sets the copyright pattern for your project, you also can use `;@currYear;` the key word in your text in aim to indicate the current year, instead of explicitly specifying).                    |                                                                                                                                                                                                                               |
 | 2    | 2.2.1    | WRONG_COPYRIGHT_YEAR                      | Checks: copyright has a valid year.<br>Fix: makes the year valid.                                                                                                                                                                                               | yes | no                                                                                                                                                                                                                         | -                                                                                                                                                                                                                             |