Bump pygments from 2.7.4 to 2.15.0 (#572)

Bumps [pygments](https://github.com/pygments/pygments) from 2.7.4 to 2.15.0.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.7.4...2.15.0)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: vincent d warmerdam <vincentwarmerdam@gmail.com>

docs-requirements.txt

@@ -3,4 +3,4 @@ sphinx_rtd_theme==0.4.3
 nbsphinx==0.4.2
 recommonmark==0.6.0
 jupyterlab-pygments==0.1.1
-pygments==2.7.4
+pygments==2.15.0