build(deps): bump pygments from 2.13.0 to 2.15.0 in /docs/.sphinx

Bumps [pygments](https://github.com/pygments/pygments) from 2.13.0 to 2.15.0.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.13.0...2.15.0)

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

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

docs/.sphinx/pinned-requirements.txt

@@ -13,7 +13,7 @@ livereload==2.6.3
 MarkupSafe==2.1.1
 packaging==21.3
 pyenchant==3.2.2
-Pygments==2.13.0
+Pygments==2.15.0
 pyparsing==3.0.9
 pytz==2022.6
 requests==2.31.0