build(deps): update pygments requirement from ~2.13.0 to ~2.15.1

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](https://github.com/pygments/pygments/commits/2.15.1)

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

Signed-off-by: dependabot[bot] <support@github.com>

pyproject.toml

@@ -8,7 +8,7 @@ license = "MIT"
 [tool.poetry.dependencies]
 python = "^3.7"
 misaka = "~2.1.1"
-Pygments = "~2.13.0"
+Pygments = "~2.15.1"
 
 [tool.poetry.dev-dependencies]
 coverage = "^6.4.2"