Docs: Fix return type for WP_HTML_Decoder::read_character_reference().

Developed in #8945

Follow-up to [58281].

Props justlevine.
See #64238, #61072.


git-svn-id: https://develop.svn.wordpress.org/trunk@61283 602fd350-edb4-49c9-b593-d223f7449a82

Author: westonruter

src/wp-includes/html-api/class-wp-html-decoder.php

@@ -203,7 +203,7 @@ public static function decode( $context, $text ): string {
 	 * @param int    $at                 Optional. Byte offset into text where span begins, defaults to the beginning (0).
 	 * @param int    &$match_byte_length Optional. Set to byte-length of character reference if provided and if a match
 	 *                                   is found, otherwise not set. Default null.
-	 * @return string|false Decoded character reference in UTF-8 if found, otherwise `false`.
+	 * @return ?string Decoded character reference in UTF-8 if found, otherwise null.
 	 */
 	public static function read_character_reference( $context, $text, $at = 0, &$match_byte_length = null ) {
 		/**