[Fix rubocop#1286] Mark Rails/SkipsModelValidations as unsafe

Fixes rubocop#1286.

`Rails/SkipsModelValidations` cop is unsafe if the receiver object is not an Active Record object.
So, this PR marks `SkipsModelValidations` as unsafe.

changelog/change_mark_rails_skips_model_validations_as_unsafe.md

@@ -0,0 +1 @@
+* [#1286](https://github.com/rubocop/rubocop-rails/issues/1286): Mark `Rails/SkipsModelValidations` as unsafe. ([@koic][])

config/default.yml

@@ -1018,8 +1018,9 @@ Rails/SkipsModelValidations:
                  See reference for more information.
   Reference: 'https://guides.rubyonrails.org/active_record_validations.html#skipping-validations'
   Enabled: true
+  Safe: false
   VersionAdded: '0.47'
-  VersionChanged: '2.7'
+  VersionChanged: '<<next>>'
   ForbiddenMethods:
     - decrement!
     - decrement_counter

lib/rubocop/cop/rails/skips_model_validations.rb

@@ -9,6 +9,9 @@ module Rails
       #
       # Methods may be ignored from this rule by configuring a `AllowedMethods`.
       #
+      # @safety
+      #   This cop is unsafe if the receiver object is not an Active Record object.
+      #
       # @example
       #   # bad
       #   Article.first.decrement!(:view_count)