Bump types-python-dateutil from 2.9.0.20251115 to 2.9.0.20260408

Bumps [types-python-dateutil](https://github.com/python/typeshed) from 2.9.0.20251115 to 2.9.0.20260408.
- [Commits](https://github.com/python/typeshed/commits)

---
updated-dependencies:
- dependency-name: types-python-dateutil
  dependency-version: 2.9.0.20260408
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

pyproject.toml

@@ -89,7 +89,7 @@ dev-mypy = [
   "frequenz-client-dispatch[cli,dev-mkdocs,dev-noxfile,dev-pytest]",
   "grpc-stubs == 1.53.0.6",
   "types-protobuf == 7.34.1.20260408",
-  "types-python-dateutil == 2.9.0.20251115",
+  "types-python-dateutil == 2.9.0.20260408",
 ]
 dev-noxfile = ["nox == 2026.4.10", "frequenz-repo-config[lib] == 0.17.0"]
 dev-pylint = [