Update pygments requirement from ~=2.4 to ~=2.19

Updates the requirements on [pygments](https://github.com/pygments/pygments) to permit the latest version.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.4.0...2.19.1)

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

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

docs/requirements.txt

@@ -4,7 +4,7 @@ sphinx >=5.0
 recommonmark ~=0.7
 pygments-style-monokailight ~=0.4
 ipython ~=7.19
-pygments ~=2.4
+pygments ~=2.19
 nbsphinx ~=0.8
 sphinxcontrib-jquery ~=4.1
 sphinx-design