Update pytest-mypy-plugins requirement from >=3.0.0 to >=4.0.3

Updates the requirements on [pytest-mypy-plugins](https://github.com/TypedDjango/pytest-mypy-plugins) to permit the latest version.
- [Release notes](https://github.com/TypedDjango/pytest-mypy-plugins/releases)
- [Changelog](https://github.com/typeddjango/pytest-mypy-plugins/blob/master/CHANGELOG.md)
- [Commits](typeddjango/pytest-mypy-plugins@3.0.0...4.0.3)

---
updated-dependencies:
- dependency-name: pytest-mypy-plugins
  dependency-version: 4.0.3
  dependency-type: direct:development
...

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

Author: dependabot[bot]

pyproject.toml

@@ -40,7 +40,7 @@ ci = [
     "pyyaml>=6.0.3",
     "types-pyyaml>=6.0.12.20250915",
     "flask>=3.1.2",
-    "pytest-mypy-plugins>=3.0.0",
+    "pytest-mypy-plugins>=4.0.3",
     "ruff>=0.14.10",
 ]
 docs = [