Post 1.56.0 release tidy up (#12379)

changelog.d/12320.misc

-Bump the version of `black` for compatibility with the latest `click` release.

changelog.d/12379.misc

+Remove temporary pin of signedjson<=1.1.1 that was added in Synapse 1.56.0.

synapse/python_dependencies.py

@@ -48,7 +48,7 @@ REQUIREMENTS = [
     "unpaddedbase64>=1.1.0",
     "canonicaljson>=1.4.0",
     # we use the type definitions added in signedjson 1.1.
-    "signedjson>=1.1.0,<=1.1.1",
+    "signedjson>=1.1.0",
     "pynacl>=1.2.1",
     "idna>=2.5",
     # validating SSL certs for IP addresses requires service_identity 18.1.