Attempt to make default config more consistent

The general idea here is that config examples should just have a hash and no
extraneous whitespace, both to make it easier for people who don't understand
yaml, and to make the examples stand out from the comments.

synapse/config/api.py

@@ -33,6 +33,7 @@ class ApiConfig(Config):
         ## API Configuration ##
 
         # A list of event types that will be included in the room_invite_state
+        #
         room_invite_state_types:
             - "{JoinRules}"
             - "{CanonicalAlias}"