Bump pymdown-extensions from 10.12 to 10.16.1 in /docs

Bumps [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions) from 10.12 to 10.16.1.
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](facelessuser/pymdown-extensions@10.12...10.16.1)

---
updated-dependencies:
- dependency-name: pymdown-extensions
  dependency-version: 10.16.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

docs/requirements.txt

@@ -65,7 +65,7 @@ pygments==2.18.0
     # via
     #   -r requirements.in
     #   mkdocs-material
-pymdown-extensions==10.12
+pymdown-extensions==10.16.1
     # via
     #   -r requirements.in
     #   mkdocs-material