chore(deps): update devdependency postcss to v8.4.31 [security]

Author: renovate[bot]

nuxt/package-lock.json

@@ -53,7 +53,7 @@
     "jest": "^29.3.1",
     "jest-environment-jsdom": "^29.3.1",
     "lint-staged": "^13.0.3",
-    "postcss": "8.4.19",
+    "postcss": "8.4.31",
     "start-server-and-test": "^1.14.0",
     "stylelint": "^14.15.0",
     "stylelint-config-prettier": "^9.0.4",