[pre-commit.ci] pre-commit autoupdate (#242)

updates:
- [github.com/psf/black: 21.8b0 → 21.9b0](psf/black@21.8b0...21.9b0)
- [github.com/asottile/pyupgrade: v2.26.0 → v2.28.0](asottile/pyupgrade@v2.26.0...v2.28.0)

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

@@ -13,7 +13,7 @@ repos:
   hooks:
   - id: isort
 - repo: https://github.com/psf/black
-  rev: '21.8b0'
+  rev: '21.9b0'
   hooks:
     - id: black
       language_version: python3 # Should be a command that runs python3.6+
@@ -41,7 +41,7 @@ repos:
     files: |
       .gitignore
 - repo: https://github.com/asottile/pyupgrade
-  rev: 'v2.26.0'
+  rev: 'v2.28.0'
   hooks:
   - id: pyupgrade
     args: ['--py36-plus']