Bump pymdown-extensions from 10.0 to 10.3.1 (#188)

Bumps [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions) from 10.0 to 10.3.1.
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](https://github.com/facelessuser/pymdown-extensions/compare/10.0...10.3.1)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements-docs.txt

@@ -1,6 +1,6 @@
 mkdocs==1.4.2
 mkdocs-material==9.1.21
-pymdown-extensions==10.0
+pymdown-extensions==10.3.1
 mike==1.1.2
 mkdocs-simple-hooks==0.1.5
 mkdocs-git-revision-date-plugin==0.3.2