build(deps-dev): update flake8-requirements requirement

Updates the requirements on [flake8-requirements](https://github.com/Arkq/flake8-requirements) to permit the latest version.
- [Commits](arkq/flake8-requirements@v2.0.1...v2.1.0)

---
updated-dependencies:
- dependency-name: flake8-requirements
  dependency-type: direct:development
...

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

Author: dependabot[bot]

requirements-dev.txt

@@ -22,7 +22,7 @@ flake8-mutable ~= 1.2
 flake8-pep3101 ~= 2.1
 flake8-print ~= 5.0
 flake8-quotes ~= 3.4
-flake8-requirements ~= 2.0
+flake8-requirements ~= 2.1
 flake8-string-format ~= 0.3
 flake8-variables-names == 0.0.6
 pytest ~= 8.0