fix(deps): update nextra monorepo to v4

Author: renovate[bot]

docs/package.json

@@ -12,8 +12,8 @@
   "dependencies": {
     "@vercel/analytics": "^1.0.0",
     "next": "14.2.0",
-    "nextra": "3.2.0",
-    "nextra-theme-docs": "3.2.0",
+    "nextra": "4.0.2",
+    "nextra-theme-docs": "4.0.2",
     "react": "18.3.1",
     "react-dom": "18.3.1"
   },