load_subreddits: Don't load 'contributor' SRMembers.

Used for Comment.add_props to see if user can reply to a comment.
That can be looked up if/when it's needed. Also used for
Builder.must_skip to check if the user can view but only if the
Subreddit is private, so also can be looked up when it's needed.

r2/r2/models/subreddit.py

@@ -617,8 +617,7 @@ class Subreddit(Thing, Printable, BaseSite):
 
         if subreddits and c.user_is_loggedin:
             # dict( {Subreddit,Account,name} -> Relationship )
-            SRMember._fast_query(subreddits.values(), (c.user,),
-                                 ('contributor', 'moderator'),
+            SRMember._fast_query(subreddits.values(), (c.user,), ('moderator',),
                                  data=True)
 
         return subreddits if return_dict else subreddits.values()