build(deps): bump pygments from 2.12 to 2.15.0

Bumps [pygments](https://github.com/pygments/pygments) from 2.12 to 2.15.0.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.12.0...2.15.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements-mkdocs.txt

@@ -18,7 +18,7 @@ mkdocs-material==7.0.6
 mkdocs-material-extensions==1.0.3
 mkdocs-minify-plugin==0.3.0
 nltk==3.6.6
-Pygments==2.12
+Pygments==2.15.0
 pymdown-extensions==10.0
 python-dateutil==2.8.1
 pytz==2020.5