Update Next.js demos to 14.2.3 (#772)

Author: xenova

examples/next-client/package-lock.json

@@ -13,7 +13,7 @@
     "autoprefixer": "10.4.14",
     "eslint": "8.45.0",
     "eslint-config-next": "13.4.12",
-    "next": "^13.5.4",
+    "next": "^14.2.3",
     "postcss": "8.4.31",
     "react": "18.2.0",
     "react-dom": "18.2.0",