Bump pygments from 2.13.0 to 2.20.0 in /docs

Bumps [pygments](https://github.com/pygments/pygments) from 2.13.0 to 2.20.0.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.13.0...2.20.0)

---
updated-dependencies:
- dependency-name: pygments
  dependency-version: 2.20.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

docs/requirements.txt

@@ -15,7 +15,7 @@ mdurl==0.1.2
 myst-parser==0.18.0
 packaging==21.3
 pipreqs==0.4.12
-Pygments==2.13.0
+Pygments==2.20.0
 pyparsing==3.0.9
 pytz==2022.2.1
 PyYAML==6.0