build(deps-dev): bump qunit from 2.20.1 to 2.21.0

Bumps [qunit](https://github.com/qunitjs/qunit) from 2.20.1 to 2.21.0.
- [Release notes](https://github.com/qunitjs/qunit/releases)
- [Changelog](https://github.com/qunitjs/qunit/blob/main/History.md)
- [Commits](https://github.com/qunitjs/qunit/compare/2.20.1...2.21.0)

---
updated-dependencies:
- dependency-name: qunit
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

package.json

@@ -37,7 +37,7 @@
     "gettext-parser": "8.0.0",
     "htmlparser": "1.7.7",
     "jed": "1.1.1",
-    "qunit": "2.20.1",
+    "qunit": "2.21.0",
     "sass": "1.77.2",
     "stylelint": "16.6.1",
     "stylelint-config-standard": "36.0.0",