Update dependency postcss to ^8.4.20

Author: renovate[bot]

package-lock.json

@@ -28,7 +28,7 @@
     "graphql": "^16.6.0",
     "next": "^13.0.6",
     "nprogress": "^0.2.0",
-    "postcss": "^8.4.19",
+    "postcss": "^8.4.20",
     "react": "18.2.0",
     "react-dom": "18.2.0",
     "react-hook-form": "^7.40.0",