Add rule for empty comments

[MAILPOET-2090]

lib/Config/Menu.php

@@ -395,7 +395,6 @@ class Menu {
       'mailpoet-experimental',
       [$this, 'experimentalFeatures']
     );
-    //
   }
 
   function disableWPEmojis() {

tasks/code_sniffer/MailPoet/ruleset.xml

@@ -5,6 +5,8 @@
 
   <!-- checks for unused methods, unused or write-only properties in a class and unused private constants -->
   <rule ref="SlevomatCodingStandard.Classes.UnusedPrivateElements"/>
+  <!-- Reports empty comments -->
+  <rule ref="SlevomatCodingStandard.Commenting.EmptyComment"/>
   <!-- This sniff enforces trailing commas in multi-line arrays -->
   <rule ref="SlevomatCodingStandard.Arrays.TrailingArrayComma"/>
   <!-- Disallows assignments in if, elseif and do-while loop conditions -->