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, 1 insertions, 1 deletions

diff --git a/synapse/metrics/_exposition.py b/synapse/metrics/_exposition.py

index 734271e765..71320a1402 100644
--- a/synapse/metrics/_exposition.py
+++ b/synapse/metrics/_exposition.py
@@ -216,7 +216,7 @@ class MetricsHandler(BaseHTTPRequestHandler):
     @classmethod
     def factory(cls, registry):
         """Returns a dynamic MetricsHandler class tied
-           to the passed registry.
+        to the passed registry.
         """
         # This implementation relies on MetricsHandler.registry
         #  (defined above and defaulted to REGISTRY).