Bump pymdown-extensions in the pip group across 1 directory

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


Updates `pymdown-extensions` from 10.20 to 10.21.3
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](facelessuser/pymdown-extensions@10.20...10.21.3)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -30,7 +30,7 @@ nltk==3.9.4
 pandas==2.3.3
 pep562==1.1
 Pygments==2.20.0
-pymdown-extensions==10.20
+pymdown-extensions==10.21.3
 python-dateutil==2.9.0.post0
 pytz==2025.2
 PyYAML==6.0.3