Update dependency postcss to v8.5.6

Author: renovate[bot]

package.json

@@ -99,7 +99,7 @@
     "jest": "29.3.0",
     "jest-transform-css": "4.0.1",
     "node-sass": "7.0.1",
-    "postcss": "8.4.20",
+    "postcss": "8.5.6",
     "react-test-renderer": "18.2.0",
     "rollup": "2.79.1",
     "rollup-plugin-filesize": "9.1.2",