Update pre-commit requirement from ~=2.19 to ~=2.20

Updates the requirements on [pre-commit](https://github.com/pre-commit/pre-commit) to permit the latest version.
- [Release notes](https://github.com/pre-commit/pre-commit/releases)
- [Changelog](https://github.com/pre-commit/pre-commit/blob/main/CHANGELOG.md)
- [Commits](pre-commit/pre-commit@v2.19.0...v2.20.0)

---
updated-dependencies:
- dependency-name: pre-commit
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements_test.txt

@@ -2,7 +2,7 @@
 -r requirements_test_min.txt
 coveralls~=3.3
 coverage~=6.4
-pre-commit~=2.19
+pre-commit~=2.20
 tbump~=6.9.0
 contributors-txt>=0.7.3
 pytest-cov~=3.0