[pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/psf/black: 21.5b2 → 21.6b0](psf/black@21.5b2...21.6b0)

Author: pre-commit-ci[bot]

.pre-commit-config.yaml

@@ -4,7 +4,7 @@ repos:
     hooks:
       - id: reorder-python-imports
   - repo: https://github.com/psf/black
-    rev: 21.5b2
+    rev: 21.6b0
     hooks:
       - id: black
         language_version: python3