Add an "others" key for Likes notifications

- Adds a key I overlooked in the reorganization.

extensions/lang-english/locale/flarum-likes.yml

@@ -17,6 +17,7 @@ flarum-likes:
     # These strings are used by the Notifications dropdown, a.k.a. "the bell".
     notifications:
       post_liked_text: "{username} liked your post"
+      others_text: => core.ref.some_others
 
     # These strings are displayed beneath individual posts.
     post: