Coding Standards: Remove extra comma in a compact() call.

This fixes a PHP compatibility error in `wp_handle_comment_submission()`:

* `Trailing comma's are not allowed in function calls in PHP 7.2 or earlier`

Follow-up to [53729].

See #55647, #56244.

git-svn-id: https://develop.svn.wordpress.org/trunk@53730 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/comment.php

@@ -3596,7 +3596,7 @@ function wp_handle_comment_submission( $comment_data ) {
 		'comment_author_url',
 		'comment_content',
 		'comment_type',
-		'comment_parent',
+		'comment_parent'
 	);
 
 	/**