build(deps): bump pygments from 2.15.1 to 2.16.1 in /docs

Bumps [pygments](https://github.com/pygments/pygments) from 2.15.1 to 2.16.1.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.15.1...2.16.1)

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

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

docs/requirements.txt

@@ -9,7 +9,7 @@ imagesize==1.4.1
 Jinja2==3.1.2
 MarkupSafe==2.1.3
 packaging==23.1
-Pygments==2.15.1
+Pygments==2.16.1
 pyparsing==3.1.1
 pytz==2023.3
 recommonmark==0.7.1