build(deps-dev): bump flake8-datetimez from 20.10.0 to 26.8.1

Bumps [flake8-datetimez](https://github.com/pjknkda/flake8-datetimez) from 20.10.0 to 26.8.1.
- [Release notes](https://github.com/pjknkda/flake8-datetimez/releases)
- [Commits](pjknkda/flake8-datetimez@20.10.0...26.8.1)

---
updated-dependencies:
- dependency-name: flake8-datetimez
  dependency-version: 26.8.1
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

pyproject.toml

@@ -47,7 +47,7 @@ email = "floss@frequenz.com"
 [project.optional-dependencies]
 dev-flake8 = [
   "flake8 == 7.3.0",
-  "flake8-datetimez == 20.10.0",
+  "flake8-datetimez == 26.8.1",
   "flake8-docstrings == 1.7.0",
   "flake8-pyproject == 1.2.4", # For reading the flake8 config from pyproject.toml
   "pydoclint == 0.9.1",