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

tests/handlers/test_federation.py

@@ -226,12 +226,20 @@ class FederationTestCase(unittest.HomeserverTestCase):
         for i in range(3):
             event = create_invite()
             self.get_success(
-                self.handler.on_invite_request(other_server, event, event.room_version,)
+                self.handler.on_invite_request(
+                    other_server,
+                    event,
+                    event.room_version,
+                )
             )
 
         event = create_invite()
         self.get_failure(
-            self.handler.on_invite_request(other_server, event, event.room_version,),
+            self.handler.on_invite_request(
+                other_server,
+                event,
+                event.room_version,
+            ),
             exc=LimitExceededError,
         )