build(deps-dev): bump cssnano from 6.1.2 to 7.0.6

Bumps [cssnano](https://github.com/cssnano/cssnano) from 6.1.2 to 7.0.6.
- [Release notes](https://github.com/cssnano/cssnano/releases)
- [Commits](https://github.com/cssnano/cssnano/compare/[email protected]@7.0.6)

---
updated-dependencies:
- dependency-name: cssnano
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

package.json

@@ -50,7 +50,7 @@
     "bootstrap5": "npm:bootstrap@^5.3.2",
     "broken-link-checker": "^0.7.8",
     "chai": "^4.3.10",
-    "cssnano": "^6.0.0",
+    "cssnano": "^7.0.6",
     "grunt": "^1.6.1",
     "grunt-cli": "^1.3.2",
     "grunt-contrib-clean": "^2.0.1",