Bump pygments in /third_party in the pip-dependencies group

Bumps the pip-dependencies group in /third_party with 1 update: [pygments](https://github.com/pygments/pygments).


Updates `pygments` from 2.19.2 to 2.20.0
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.19.2...2.20.0)

---
updated-dependencies:
- dependency-name: pygments
  dependency-version: 2.20.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: pip-dependencies
...

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

Author: dependabot[bot]

third_party/requirements.txt

@@ -8,7 +8,7 @@ bandit==1.9.4
 # Tests
 packaging==26.0
 # Generating HTML documentation
-pygments==2.19.2
+pygments==2.20.0
 sphinxcontrib_applehelp==2.0.0
 sphinxcontrib_devhelp==2.0.0
 sphinxcontrib_htmlhelp==2.1.0