Fix initialization for "preprocess_comment" filter (#552) (#553)

This is a filter hook, so we should initialize it using `add_filter()`
instead of `add_action()`.

antispam_bee.php

@@ -330,7 +330,7 @@ public static function init() {
 					'precheck_incoming_request',
 				)
 			);
-			add_action(
+			add_filter(
 				'preprocess_comment',
 				array(
 					__CLASS__,