Bump postcss to 8.5.4 (#4997)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

docs/package.json

@@ -69,7 +69,7 @@
     "markdown-to-jsx": "7.7.6",
     "next": "^15.3.2",
     "nprogress": "0.2.0",
-    "postcss": "8.4.49",
+    "postcss": "8.5.4",
     "prismjs": "1.30.0",
     "prop-types": "15.8.1",
     "react": "^19.1.0",