build(deps-dev): bump flake8-simplify from 0.20.0 to 0.21.0

Bumps [flake8-simplify](https://github.com/MartinThoma/flake8-simplify) from 0.20.0 to 0.21.0.
- [Release notes](https://github.com/MartinThoma/flake8-simplify/releases)
- [Changelog](https://github.com/MartinThoma/flake8-simplify/blob/main/CHANGELOG.md)
- [Commits](https://github.com/MartinThoma/flake8-simplify/commits/0.21.0)

---
updated-dependencies:
- dependency-name: flake8-simplify
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

pyproject.toml

@@ -74,7 +74,7 @@ dev = [
     "flake8-no-implicit-concat==0.3.4",
     "flake8-print==5.0.0",
     "flake8-todos==0.3.0",
-    "flake8-simplify==0.20.0",
+    "flake8-simplify==0.21.0",
     "flake8-use-pathlib==0.3.0",
     "flake8-copyright==0.2.4",
     "ruff==0.0.291",