[pre-commit.ci] pre-commit autoupdate (#24)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: pre-commit-ci[bot]

.pre-commit-config.yaml

@@ -18,7 +18,7 @@ repos:
     hooks:
       - id: isort
   - repo: https://github.com/psf/black
-    rev: 21.8b0
+    rev: 21.9b0
     hooks:
       - id: black
         args: [--safe]