chore(deps): bump pymdown-extensions in /hack/api-docs (#6157)

Bumps [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions) from 10.21 to 10.21.2.
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](https://github.com/facelessuser/pymdown-extensions/compare/10.21...10.21.2)

---
updated-dependencies:
- dependency-name: pymdown-extensions
  dependency-version: 10.21.2
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

hack/api-docs/requirements.txt

@@ -27,7 +27,7 @@ pathspec==1.0.4
 pep562==1.1
 platformdirs==4.9.4
 Pygments==2.19.2
-pymdown-extensions==10.21
+pymdown-extensions==10.21.2
 python-dateutil==2.9.0.post0
 PyYAML==6.0.3
 pyyaml_env_tag==1.1