Bump pymdown-extensions from 10.6 to 10.8

Bumps [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions) from 10.6 to 10.8.
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](facelessuser/pymdown-extensions@10.6...10.8)

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

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

requirements-docs.txt

@@ -1,6 +1,6 @@
 mkdocs==1.5.3
 mkdocs-material==9.5.14
-pymdown-extensions==10.6
+pymdown-extensions==10.8
 mike==2.0.0
 mkdocs-simple-hooks==0.1.5
 mkdocs-git-revision-date-plugin==0.3.2