Fix a number of issues:

1) formatting;
2) "gzip, GZIP" is ok for they case-insensitive match.
3) there is a mistake saying that the "contentEncoding" consists of
digits;
4) no longer returns "contentEncoding" for data url.

fetch.bs

@@ -3973,12 +3973,10 @@ extract an encoding type</dfn> from a <a for=/>header list</a> <var>headers</var
    <li><p>If <var>candidateValue</var> is null, then set <var>candidateValue</var> to
    <var>value</var>.
 
-   <li><p>Otherwise, if <var>value</var> is not <var>candidateValue</var>, return failure.
+   <li><p>Otherwise, if <var>value</var> is not an <a>ASCII case-insensitive</a> match for
+   <var>candidateValue</var>, return failure.
   </ol>
 
- <li><p>If <var>candidateValue</var> is the empty string or has a <a for=/>code point</a> that is
- not an <a for=/>ASCII digit</a>, then return null.
-
  <li><p>Return <var>candidateValue</var>, interpreted as a string.
 </ol>
 </div>
@@ -5047,12 +5045,12 @@ steps:
 
      <li><p>Let <var>coding</var> be the empty string.
 
-     <li><p>Let <var>accept-coding</var> be the result of <a for="header list">getting</a>
-        `<code>Accept-Encoding</code>` from <var>request</var>'s <a for=request>header list</a>.
-        If <var>accept-encoding</var> is not null and the server selects one of the encoding options,
-        set <var>coding</var> to the selected encoding option; otherwise, i.e., no encoding is used,
-        set <var>coding</var> to <a href=https://httpwg.org/specs/rfc9110.html#field.accept-encoding>
-        <code>"identity"</code></a>.
+     <li><p>Let <var>accept-encoding</var> be the result of <a for="header list">getting</a>
+     `<code>Accept-Encoding</code>` from <var>request</var>'s <a for=request>header list</a>.
+     If <var>accept-encoding</var> is not null and the server selects one of the encoding options,
+     set <var>coding</var> to the selected encoding option; otherwise, i.e., no encoding is used,
+     set <var>coding</var> to <a href=https://httpwg.org/specs/rfc9110.html#field.accept-encoding>
+     <code>"identity"</code></a>.
 
      <li>
       <p>If <var>request</var>'s <a for=request>header list</a>
@@ -5158,20 +5156,10 @@ steps:
      <li><p>Let <var>mimeType</var> be <var>dataURLStruct</var>'s
      <a for="data: URL struct">MIME type</a>, <a lt="serialize a MIME type to bytes">serialized</a>.
 
-     <li><p>Let <var>coding</var> be the empty string.
-
-     <li><p>Let <var>accept-coding</var> be the result of <a for="header list">getting</a>
-        `<code>Accept-Encoding</code>` from <var>request</var>'s <a for=request>header list</a>.
-        If <var>accept-encoding</var> is not null and the server selects one of the encoding options,
-        set <var>coding</var> to the selected encoding option; otherwise, i.e., no encoding is used,
-        set <var>coding</var> to <a href=https://httpwg.org/specs/rfc9110.html#field.accept-encoding>
-        <code>"identity"</code></a>.
-
      <li><p>Return a new <a for=/>response</a> whose <a for=response>status message</a> is
      `<code>OK</code>`, <a for=response>header list</a> is « (`<code>Content-Type</code>`,
-     <var>mimeType</var>), (`<code>Content-Encoding</code>`, <var>coding</var>) », and
-     <a for=response>body</a> is <var>dataURLStruct</var>'s <a for="data: URL struct">
-     body</a> <a for="byte sequence">as a body</a>.
+     <var>mimeType</var>) », and <a for=response>body</a> is <var>dataURLStruct</var>'s
+     <a for="data: URL struct">body</a> <a for="byte sequence">as a body</a>.
 
     </ol>