ci(pre-commit.ci): pre-commit autoupdate (#12)

updates:
- [github.com/psf/black: 21.6b0 → 21.7b0](psf/black@21.6b0...21.7b0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

.pre-commit-config.yaml

@@ -17,7 +17,7 @@ repos:
     -   id: mixed-line-ending
     -   id: trailing-whitespace
 -   repo: https://github.com/psf/black
-    rev: 21.6b0
+    rev: 21.7b0
     hooks:
     -   id: black
         exclude: (.*)/migrations