Improving on modtools by giving usernotes space

Toolbox usernotes often run out of space for subreddits relying heavily on
them. These are also the subreddits that form a positive image about reddit
since they are often very well moderated.

This will allow these subreddits to use toolbox usernotes properly.

r2/r2/models/wiki.py

@@ -79,7 +79,8 @@ special_length_restrictions_bytes = {
     'config/stylesheet': 128*1024,
     'config/submit_text': 1024,
     'config/sidebar': 5120,
-    'config/description': 500
+    'config/description': 500,
+    'usernotes': 1024*1024,
 }
 
 modactions = {