fix(docs): bump docus to 5.9.0 for og-image v6 compat

docus 5.8.1 has OG image components without the v6 renderer suffix,
which breaks the docs build with nuxt-og-image 6.x.

Author: harlan-zw

docs/package.json

@@ -22,7 +22,7 @@
     "@nuxt/ui": "4.5.1",
     "@nuxtjs/mdc": "0.20.2",
     "better-sqlite3": "12.8.0",
-    "docus": "5.8.1",
+    "docus": "5.9.0",
     "nuxt": "4.3.1",
     "tailwindcss": "4.2.2"
   }