Update dependency stylelint to v16.21.0 (#1421)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package.json

@@ -96,7 +96,7 @@
     "release-plan": "^0.13.1",
     "rsvp": "4.8.5",
     "sinon": "21.0.0",
-    "stylelint": "16.20.0",
+    "stylelint": "16.21.0",
     "stylelint-config-standard": "38.0.0",
     "stylelint-prettier": "5.0.3",
     "webpack": "5.99.9"