Bump pymdown-extensions from 10.3.1 to 10.16.1 in /docs (#115)

Bumps [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions) from 10.3.1 to 10.16.1.
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](facelessuser/pymdown-extensions@10.3.1...10.16.1)

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

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Author: dependabot[bot]

docs/requirements.txt

@@ -4,4 +4,4 @@ mkdocs==1.5.3
 mkdocs-glightbox==0.3.4
 mkdocs-material==9.4.6
 mkdocs-material-extensions==1.3
-pymdown-extensions==10.3.1
+pymdown-extensions==10.16.1