[mod] pre-commit black revision stick to v21.5b0

https://pre-commit.com/#pre-commit-configyaml---repos
7 jobs for readme_contributing_enh in 3 minutes and 8 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Checks
passed build #54108

00:00:27

passed format #54109

00:00:32

passed isort #54110

00:00:28

 
  Tests
passed tests-3.6 #54111
mille

00:01:38

passed tests-3.7-coverage #54112
mille

00:01:44

passed tests-3.8 #54113
redshift

00:01:32

passed tests-3.9 #54114
redshift

00:00:59