⬆️ upgrade nextra monorepo to v4

Author: renovate[bot]

package.json

@@ -12,8 +12,8 @@
   "license": "MIT",
   "dependencies": {
     "next": "^12.1.6",
-    "nextra": "^2.13.4",
-    "nextra-theme-docs": "^2.13.4",
+    "nextra": "^4.0.0",
+    "nextra-theme-docs": "^4.0.0",
     "react": "^18.2.0",
     "react-dom": "^18.2.0",
     "react-markdown": "^9.0.1",