Include correctly encoded HTML class name "&" initially

Author: sirreal

tests/phpunit/tests/html-api/wpHtmlTagProcessor.php

@@ -3032,12 +3032,9 @@ public static function data_updating_attributes_in_malformed_html() {
 	 * @ticket 64340
 	 */
 	public function test_class_changes_produce_correct_html() {
-		$processor = new WP_HTML_Tag_Processor( '<div>' );
+		$processor = new WP_HTML_Tag_Processor( '<div class="&amp;">' );
 		$processor->next_tag();
 
-		$processor->add_class( '&' );
-		$processor->get_updated_html();
-
 		$processor->add_class( '"' );
 		$processor->get_updated_html();