HTML API: Make META tag test data provider static.

Developed in WordPress#9318.

Follow-up to [60502].

Props jonsurrell, mukesh27.
See #63738.


git-svn-id: https://develop.svn.wordpress.org/trunk@60503 602fd350-edb4-49c9-b593-d223f7449a82

Author: sirreal

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

@@ -47,7 +47,7 @@ public function __construct( $html ) {
 	/**
 	 * Data provider.
 	 */
-	public function data_unsupported_meta_tags(): array {
+	public static function data_unsupported_meta_tags(): array {
 		return array(
 			'With charset'                => array( '<meta charset="utf8">', 'Cannot yet process META tags with charset to determine encoding.' ),
 			'With CHARSET'                => array( '<meta CHARSET="utf8">', 'Cannot yet process META tags with charset to determine encoding.' ),