Update requirements: Bump cssutils from 2.14.0 to 2.15.0

Bumps [cssutils](https://github.com/jaraco/cssutils) from 2.14.0 to 2.15.0.
- [Release notes](https://github.com/jaraco/cssutils/releases)
- [Changelog](https://github.com/jaraco/cssutils/blob/main/NEWS.rst)
- [Commits](jaraco/cssutils@v2.14.0...v2.15.0)

---
updated-dependencies:
- dependency-name: cssutils
  dependency-version: 2.15.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

pyproject.toml

@@ -40,7 +40,7 @@ dependencies = [
     "appdirs==1.4.4",
     "beautifulsoup4==4.14.3",
     "charset-normalizer==3.4.7",
-    "cssutils==2.14.0",
+    "cssutils==2.15.0",
     "dhash==1.4",
     "html5lib==1.1",
     "lxml==6.1.0",