Bump pymdown-extensions from 10.20.1 to 10.21.3 (#1026)

Bumps [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions) from 10.20.1 to 10.21.3.
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](https://github.com/facelessuser/pymdown-extensions/commits/10.21.3)

---
updated-dependencies:
- dependency-name: pymdown-extensions
  dependency-version: 10.21.3
  dependency-type: indirect
...

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

Author: dependabot[bot]

requirements.txt

@@ -106,7 +106,7 @@ pyee==13.0.0
     # via playwright
 pygments==2.20.0
     # via mkdocs-material
-pymdown-extensions==10.20.1
+pymdown-extensions==10.21.3
     # via mkdocs-material
 pypdf==6.10.2
     # via mkdocs-exporter