fix: specify version of next-auth (#1328)

When using the 'latest' tag, v3 of next-auth was being installed.

However, the type definitions used in the example project aren't introduced until v4.

Pinning to v4 in order to ensure expected behaviour

Author: ericapisani

demos/next-auth/package.json

@@ -23,7 +23,7 @@
   ],
   "license": "ISC",
   "dependencies": {
-    "next-auth": "latest",
+    "next-auth": "^4.3.3",
     "nodemailer": "^6.6.3",
     "react": "^17.0.2",
     "react-dom": "^17.0.2"