deps: update mypy requirement from >=1.15.0 to >=1.20.2 in /config (#36)

Updates the requirements on [mypy](https://github.com/python/mypy) to permit the latest version.
- [Changelog](https://github.com/python/mypy/blob/master/CHANGELOG.md)
- [Commits](python/mypy@v1.15.0...v1.20.2)

---
updated-dependencies:
- dependency-name: mypy
  dependency-version: 1.20.2
  dependency-type: direct:development
...

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

Author: dependabot[bot]

config/requirements-dev.txt

@@ -4,6 +4,6 @@ pytest-cov>=4.1.0
 pytest-mock>=3.15.1
 black>=25.11.0
 flake8>=6.1.0
-mypy>=1.15.0
+mypy>=1.20.2