Update black, and run auto formatting over the codebase (#9381)

- Update black version to the latest
 - Run black auto formatting over the codebase
    - Run autoformatting according to [`docs/code_style.md
`](80d6dc9783/docs/code_style.md)
 - Update `code_style.md` docs around installing black to use the correct version

synapse/appservice/__init__.py

@@ -166,7 +166,10 @@ class ApplicationService:
 
     @cached(num_args=1, cache_context=True)
     async def matches_user_in_member_list(
-        self, room_id: str, store: "DataStore", cache_context: _CacheContext,
+        self,
+        room_id: str,
+        store: "DataStore",
+        cache_context: _CacheContext,
     ) -> bool:
         """Check if this service is interested a room based upon it's membership