General: Use static on closures whenever $this is not used to avoid memory leaks.

Props westonruter, jrf, spacedmonkey.
Fixes #58323.


git-svn-id: https://develop.svn.wordpress.org/trunk@55822 602fd350-edb4-49c9-b593-d223f7449a82

tests/performance/wp-content/mu-plugins/server-timing.php

@@ -2,7 +2,7 @@
 
 add_action(
 	'template_redirect',
-	function() {
+	static function() {
 
 		global $timestart;
 
@@ -15,7 +15,7 @@ add_action(
 
 		add_action(
 			'shutdown',
-			function() use ( $server_timing_values, $template_start ) {
+			static function() use ( $server_timing_values, $template_start ) {
 
 				global $timestart;