chore(deps): update dependency postcss to v8.5.4

Author: renovate[bot]

packages/website/package.json

@@ -23,7 +23,7 @@
     "next-themes": "0.4.6",
     "nextra": "3.3.1",
     "nextra-theme-docs": "3.3.1",
-    "postcss": "8.5.3",
+    "postcss": "8.5.4",
     "postcss-lightningcss": "1.0.1",
     "react": "19.1.0",
     "react-docgen": "workspace:8.0.0",