build(deps): update pymdown-extensions requirement

Updates the requirements on [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions) to permit the latest version.
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](facelessuser/pymdown-extensions@10.8.1...10.12)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements-docs.txt

@@ -2,4 +2,4 @@ markdown-include~=0.8.1
 mkdocs~=1.6.0
 mkdocs-material~=9.5.46
 pygments~=2.18.0
-pymdown-extensions~=10.8.1
+pymdown-extensions~=10.12