deps: update flake8 requirement from >=7.0.0 to >=7.3.0

Updates the requirements on [flake8](https://github.com/pycqa/flake8) to permit the latest version.
- [Commits](PyCQA/flake8@7.0.0...7.3.0)

---
updated-dependencies:
- dependency-name: flake8
  dependency-version: 7.3.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements.txt

@@ -14,6 +14,6 @@ timezonefinder
 pre-commit>=4.6.1
 black>=26.5.1
 isort>=8.0.1
-flake8>=7.0.0
+flake8>=7.3.0
 pytest>=9.1.1
 pytest-cov>=4.1.0