HTML API: Fix typo in documentation example.

The example code in the PHPDoc comment for the HTML Tag Processor class
previously showed calling `next_tag()` with an array containing a `class`
key, which should have been `class_name`. This patch fixes this by using
the appropriate `class_name` key.

Props dmsnell, gaambo, crstauf, atachibana, audrasjb, krupalpanchal.
Fixes #59891.

git-svn-id: https://develop.svn.wordpress.org/trunk@57116 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/html-api/class-wp-html-tag-processor.php

@@ -116,7 +116,7 @@
  *
  * Example:
  *
- *     if ( $tags->next_tag( array( 'class' => 'wp-group-block' ) ) ) {
+ *     if ( $tags->next_tag( array( 'class_name' => 'wp-group-block' ) ) ) {
  *         $tags->set_attribute( 'title', 'This groups the contained content.' );
  *         $tags->remove_attribute( 'data-test-id' );
  *     }