[pre-commit.ci] pre-commit autoupdate (#136)

updates:
- [github.com/psf/black: 20.8b1 → 21.4b0](psf/black@20.8b1...21.4b0)

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

@@ -8,7 +8,7 @@ repos:
         exclude: ^docs/.*|.*.md
 
 -   repo: https://github.com/psf/black
-    rev: 20.8b1
+    rev: 21.4b0
     hooks:
     -   id: black
         language_version: python3