Coding Standards: Use static closures when not using $this.

When a closure does not use `$this`, it can be made `static` for improved performance.

Static closures are supported in PHP since PHP 5.4. ​

Props jrf, hellofromTonya, swissspidy, SergeyBiryukov.
See #53359.

git-svn-id: https://develop.svn.wordpress.org/trunk@51657 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/user.php

@@ -3459,7 +3459,7 @@ function wp_user_personal_data_exporter( $email_address ) {
 		// Remove items that use reserved names.
 		$extra_data = array_filter(
 			$_extra_data,
-			function( $item ) use ( $reserved_names ) {
+			static function( $item ) use ( $reserved_names ) {
 				return ! in_array( $item['name'], $reserved_names, true );
 			}
 		);