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
`](https://github.com/matrix-org/synapse/blob/80d6dc9783aa80886a133756028984dbf8920168/docs/code_style.md)
 - Update `code_style.md` docs around installing black to use the correct version

1 files changed, 2 insertions, 4 deletions

diff --git a/synapse/storage/purge_events.py b/synapse/storage/purge_events.py
index 6c359c1aae..3c4908865f 100644
--- a/synapse/storage/purge_events.py
+++ b/synapse/storage/purge_events.py
@@ -26,15 +26,13 @@ logger = logging.getLogger(__name__)
 
 
 class PurgeEventsStorage:
-    """High level interface for purging rooms and event history.
-    """
+    """High level interface for purging rooms and event history."""
 
     def __init__(self, hs: "HomeServer", stores: Databases):
         self.stores = stores
 
     async def purge_room(self, room_id: str) -> None:
-        """Deletes all record of a room
-        """
+        """Deletes all record of a room"""
 
         state_groups_to_delete = await self.stores.main.purge_room(room_id)
         await self.stores.state.purge_room_state(room_id, state_groups_to_delete)