Build(deps-dev): Bump find-unused-sass-variables from 5.0.0 to 6.0.0 (#39858)

Bumps [find-unused-sass-variables](https://github.com/XhmikosR/find-unused-sass-variables) from 5.0.0 to 6.0.0.
- [Release notes](https://github.com/XhmikosR/find-unused-sass-variables/releases)
- [Commits](https://github.com/XhmikosR/find-unused-sass-variables/compare/v5.0.0...v6.0.0)

---
updated-dependencies:
- dependency-name: find-unused-sass-variables
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -124,7 +124,7 @@
     "eslint-plugin-import": "^2.29.1",
     "eslint-plugin-markdown": "^4.0.1",
     "eslint-plugin-unicorn": "^51.0.1",
-    "find-unused-sass-variables": "^5.0.0",
+    "find-unused-sass-variables": "^6.0.0",
     "globby": "^14.0.1",
     "hammer-simulator": "0.0.1",
     "hugo-bin": "^0.121.1",