Bump types-python-dateutil in /tools

Bumps [types-python-dateutil](https://github.com/python/typeshed) from 2.9.0.20240316 to 2.9.0.20240906.
- [Commits](https://github.com/python/typeshed/commits)

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

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

tools/requirements_mypy.txt

@@ -4,7 +4,7 @@ toml==0.10.2
 tomli==2.0.1
 typed-ast==1.5.5
 types-atomicwrites==1.4.5.1
-types-python-dateutil==2.9.0.20240316
+types-python-dateutil==2.9.0.20240906
 types-PyYAML==6.0.12.12
 types-requests==2.32.0.20240905
 types-setuptools==69.5.0.20240423