Update pre-commit requirement from ~=2.17 to ~=2.21

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@v2.17.0...v2.21.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements_test.txt

@@ -3,7 +3,7 @@
 contributors-txt>=0.7.4
 coveralls~=3.3
 coverage~=5.5
-pre-commit~=2.17
+pre-commit~=2.21
 pytest-cov~=3.0
 contributors-txt>=0.7.3
 tbump~=6.3.2