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, 1 deletions

diff --git a/synapse/rest/media/v1/download_resource.py b/synapse/rest/media/v1/download_resource.py

index 3ed219ae43..48f4433155 100644
--- a/synapse/rest/media/v1/download_resource.py
+++ b/synapse/rest/media/v1/download_resource.py
@@ -51,7 +51,8 @@ class DownloadResource(DirectServeJsonResource):
             b" object-src 'self';",
         )
         request.setHeader(
-            b"Referrer-Policy", b"no-referrer",
+            b"Referrer-Policy",
+            b"no-referrer",
         )
         server_name, media_id, name = parse_media_id(request)
         if server_name == self.server_name: