chore: upgrade isort and fix pre-commit hook

See https://github.com/PyCQA/isort/pull/2078

Part-of: <https://dev.funkwhale.audio/funkwhale/funkwhale/-/merge_requests/2345>

.pre-commit-config.yaml

@@ -37,7 +37,7 @@ repos:
       - id: black
 
   - repo: https://github.com/pycqa/isort
-    rev: 5.10.1
+    rev: 5.12.0
     hooks:
       - id: isort