[pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/pre-commit/mirrors-prettier: v2.4.0 → v2.4.1](pre-commit/mirrors-prettier@v2.4.0...v2.4.1)
- [github.com/psf/black: 21.8b0 → 21.9b0](psf/black@21.8b0...21.9b0)

Author: pre-commit-ci[bot]

.pre-commit-config.yaml

@@ -12,7 +12,7 @@ repos:
         exclude: CHANGELOG.md
 
   - repo: https://github.com/pre-commit/mirrors-prettier
-    rev: v2.4.0
+    rev: v2.4.1
     hooks:
       - id: prettier
         files: '.*\.mdx?$'
@@ -32,6 +32,6 @@ repos:
         args: ['--in-place', '--remove-all-unused-imports', '--remove-unused-variable']
 
   - repo: https://github.com/psf/black
-    rev: 21.8b0
+    rev: 21.9b0
     hooks:
       - id: black