Bump @webref/css from 6.15.1 to 6.15.2

Bumps [@webref/css](https://github.com/w3c/webref) from 6.15.1 to 6.15.2.
- [Commits](https://github.com/w3c/webref/compare/@webref/css@6.15.1...@webref/css@6.15.2)

---
updated-dependencies:
- dependency-name: "@webref/css"
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

package.json

@@ -96,7 +96,7 @@
     "@types/webidl2": "^24.4.3",
     "@types/yargs": "^17.0.33",
     "@typescript-eslint/eslint-plugin": "7.18.0",
-    "@webref/css": "6.15.1",
+    "@webref/css": "6.15.2",
     "@webref/elements": "^2.3.0",
     "@webref/idl": "3.53.1",
     "c8": "10.1.2",