fix: upgrade stylelint-scss from 3.18.0 to 3.21.0

Snyk has created this PR to upgrade stylelint-scss from 3.18.0 to 3.21.0.

See this package in npm:
https://www.npmjs.com/package/stylelint-scss

See this project in Snyk:
https://app.snyk.io/org/yext/project/0f7d62e5-8ca2-46bd-abb0-048a1a25e0fa?utm_source=github&utm_medium=referral&page=upgrade-pr

package.json

@@ -38,7 +38,7 @@
     "lodash.isequal": "^4.5.0",
     "markdown-it-for-inline": "^0.1.1",
     "plural-forms": "^0.5.1",
-    "stylelint-scss": "^3.18.0",
+    "stylelint-scss": "^3.21.0",
     "template-helpers": "^1.0.1",
     "uuid": "^8.3.2"
   },