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_device.py

@@ -260,7 +260,9 @@ class DehydrationTestCase(unittest.HomeserverTestCase):
         # Create a new login for the user and dehydrated the device
         device_id, access_token = self.get_success(
             self.registration.register_device(
-                user_id=user_id, device_id=None, initial_display_name="new device",
+                user_id=user_id,
+                device_id=None,
+                initial_display_name="new device",
             )
         )