build(deps): bump pygments from 2.11.2 to 2.15.0 in /requirements/tox

Bumps [pygments](https://github.com/pygments/pygments) from 2.11.2 to 2.15.0.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.11.2...2.15.0)

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

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

Author: dependabot[bot]

requirements/tox/doc8_requirements.txt

@@ -1,2 +1,2 @@
 doc8==0.10.1
-Pygments==2.11.2
+Pygments==2.15.0