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/storage/databases/main/directory.py

@@ -85,7 +85,7 @@ class DirectoryStore(DirectoryWorkerStore):
         servers: Iterable[str],
         creator: Optional[str] = None,
     ) -> None:
-        """ Creates an association between a room alias and room_id/servers
+        """Creates an association between a room alias and room_id/servers
 
         Args:
             room_alias: The alias to create.
@@ -160,7 +160,10 @@ class DirectoryStore(DirectoryWorkerStore):
         return room_id
 
     async def update_aliases_for_room(
-        self, old_room_id: str, new_room_id: str, creator: Optional[str] = None,
+        self,
+        old_room_id: str,
+        new_room_id: str,
+        creator: Optional[str] = None,
     ) -> None:
         """Repoint all of the aliases for a given room, to a different room.