Add contact in list checking method

Correct third person verb form of description;

src/Snowcap/Emarsys/Client.php

@@ -418,7 +418,7 @@ public function getContactsFromContactList($listId, array $data)
     }
 
     /**
-     * Check whether a specific contact is included in the defined contact list.
+     * Checks whether a specific contact is included in the defined contact list.
      *
      * @param int $contactId
      * @param int $listId