Update dependency postcss to v8.3.9

Author: renovate-bot

javascript/package-lock.json

@@ -72,7 +72,7 @@
     "js-yaml": "4.1.0",
     "mocha": "9.1.2",
     "npm-check-updates": "11.8.5",
-    "postcss": "8.3.8",
+    "postcss": "8.3.9",
     "postcss-cli": "9.0.1",
     "prettier": "2.4.1",
     "pretty-quick": "3.1.1",