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/tests/storage/test_events.py b/tests/storage/test_events.py
index 71210ce606..ed898b8dbb 100644
--- a/tests/storage/test_events.py
+++ b/tests/storage/test_events.py
@@ -68,16 +68,14 @@ class ExtremPruneTestCase(HomeserverTestCase):
         self.assert_extremities([self.remote_event_1.event_id])
 
     def persist_event(self, event, state=None):
-        """Persist the event, with optional state
-        """
+        """Persist the event, with optional state"""
         context = self.get_success(
             self.state.compute_event_context(event, old_state=state)
         )
         self.get_success(self.persistence.persist_event(event, context))
 
     def assert_extremities(self, expected_extremities):
-        """Assert the current extremities for the room
-        """
+        """Assert the current extremities for the room"""
         extremities = self.get_success(
             self.store.get_prev_events_for_room(self.room_id)
         )