Bump pre-commit from 2.20.0 to 2.21.0 (#770)

Bumps [pre-commit](https://github.com/pre-commit/pre-commit) from 2.20.0 to 2.21.0.
- [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@v2.20.0...v2.21.0)

---
updated-dependencies:
- dependency-name: pre-commit
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

setup.py

@@ -57,7 +57,7 @@
     extras_require={
         "dev": [
             # Setup.
-            "pre-commit==2.20.0 ; python_version>='3.7'",
+            "pre-commit==2.21.0 ; python_version>='3.7'",
             "tox==3.27.1",
             # Testing framework.
             "pytest==6.1.2 ; python_version<'3.7'",