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

Author: renovate[bot]

package.json

@@ -63,7 +63,7 @@
     "lit-html": "2.8.0",
     "npm-run-all": "4.1.5",
     "playwright": "1.37.1",
-    "postcss": "8.4.29",
+    "postcss": "8.4.31",
     "postcss-cli": "10.1.0",
     "postcss-discard-comments": "5.1.2",
     "postcss-discard-empty": "5.1.1",