chore: use 2x faster black mirror (#456)

Committed via https://github.com/asottile/all-repos

Author: henryiii

.pre-commit-config.yaml

@@ -28,7 +28,7 @@ repos:
       - id: rst-directive-colons
       - id: rst-inline-touching-normal
 
-  - repo: https://github.com/psf/black
+  - repo: https://github.com/psf/black-pre-commit-mirror
     rev: 23.7.0
     hooks:
       - id: black-jupyter