chore(deps): bump pymdown-extensions in the uv group across 1 directory

Bumps the uv group with 1 update in the / directory: [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions).


Updates `pymdown-extensions` from 10.16.1 to 10.21.3
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](facelessuser/pymdown-extensions@10.16.1...10.21.3)

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

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Author: dependabot[bot]