Update text/html registration

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@@ -114193,10 +114193,9 @@ interface <dfn>External</dfn> {
 
       <p>The <code data-x="">charset</code> parameter may be provided to specify the
       <span>document's character encoding</span>, overriding any <span data-x="character encoding
-      declaration">character encoding declarations</span> in the document other than a Byte Order Mark (BOM). The parameter's value
-      must be one of the <span data-x="encoding label">labels</span> of the <span
-      data-x="encoding">character encoding</span> used to serialize the file. <ref
-      spec=ENCODING></p>
+      declaration">character encoding declarations</span> in the document other than a Byte Order
+      Mark (BOM). The parameter's value must be an <span>ASCII case-insensitive</span> match for the
+      string "<code data-x="">utf-8</code>". <ref spec=ENCODING></p>
 
      </dd>
     </dl>