Bump pygments from 2.14.0 to 2.15.0 in /docs

Bumps [pygments](https://github.com/pygments/pygments) from 2.14.0 to 2.15.0.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.14.0...2.15.0)

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

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

docs/requirements.txt

@@ -10,7 +10,7 @@ imagesize==1.4.1
 Jinja2==3.1.2
 MarkupSafe==2.1.2
 packaging==23.0
-Pygments==2.14.0
+Pygments==2.15.0
 pytz==2022.7.1
 requests==2.28.2
 snowballstemmer==2.2.0