[pre-commit.ci] pre-commit autoupdate (#13)

updates:
- [github.com/psf/black: 21.7b0 → 21.9b0](psf/black@21.7b0...21.9b0)

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

.pre-commit-config.yaml

@@ -38,7 +38,7 @@ repos:
 
 # Python formatting
 - repo: https://github.com/psf/black
-  rev: 21.7b0
+  rev: 21.9b0
   hooks:
   - id: black