[pre-commit.ci] pre-commit autoupdate (jpadilla#656)

updates:
- [github.com/psf/black: 21.4b0 → 21.4b2](psf/black@21.4b0...21.4b2)

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

@@ -1,6 +1,6 @@
 repos:
   - repo: https://github.com/psf/black
-    rev: 21.4b0
+    rev: 21.4b2
     hooks:
       - id: black
         args: ["--target-version=py36"]