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/handlers/admin.py b/synapse/handlers/admin.py
index 37e63da9b1..db68c94c50 100644
--- a/synapse/handlers/admin.py
+++ b/synapse/handlers/admin.py
@@ -203,13 +203,11 @@ class AdminHandler(BaseHandler):
 
 
 class ExfiltrationWriter(metaclass=abc.ABCMeta):
-    """Interface used to specify how to write exported data.
-    """
+    """Interface used to specify how to write exported data."""
 
     @abc.abstractmethod
     def write_events(self, room_id: str, events: List[EventBase]) -> None:
-        """Write a batch of events for a room.
-        """
+        """Write a batch of events for a room."""
         raise NotImplementedError()
 
     @abc.abstractmethod