chore: bump postcss

Author: nikku

package-lock.json

@@ -13,7 +13,7 @@
     "min-dash": "^4.2.3",
     "npm-run-all2": "^8.0.4",
     "octicons": "^8.5.0",
-    "postcss": "^8.4.49",
+    "postcss": "^8.5.6",
     "rollup": "^4.52.4",
     "rollup-plugin-copy": "^3.5.0",
     "rollup-plugin-css-only": "^4.5.5",