Bump pymdown-extensions from 10.8.1 to 10.9 in /.github

Bumps [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions) from 10.8.1 to 10.9.
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](facelessuser/pymdown-extensions@10.8.1...10.9)

---
updated-dependencies:
- dependency-name: pymdown-extensions
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

.github/workflows/requirements.txt

@@ -5,7 +5,7 @@ mdx_truly_sane_lists==1.3
 mkdocs==1.6.0
 pygccxml==2.5.0
 Pygments==2.18.0
-pymdown-extensions==10.8.1
+pymdown-extensions==10.9
 pyplusplus==1.8.5
 setuptools==72.1.0
 six==1.16.0