Update pygments requirement from <=2.13.0,>=2.7.4 to >=2.7.4,<=2.18.0

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@2.7.4...2.18.0)

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

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

Author: dependabot[bot]

tests/requirements.txt

@@ -4,7 +4,7 @@ coincidence>=0.2.0
 coverage>=5.1
 coverage-pyver-pragma>=0.2.1
 importlib-metadata>=3.6.0
-pygments<=2.13.0,>=2.7.4
+pygments>=2.7.4,<=2.18.0
 pytest>=6.0.0
 pytest-cov>=2.8.1
 pytest-randomly>=3.7.0