remove vercel legacy config

vercel.json

@@ -1,9 +1,24 @@
 {
-  "version": 2,
+  "rewrites": [
-  "builds": [
     {
-      "src": "package.json",
+      "source": "/old-path",
-      "use": "@vercel/next"
+      "destination": "/new-path"
+    }
+  ],
+  "headers": [
+    {
+      "source": "/(.*)",
+      "headers": [
+        {
+          "key": "X-Custom-Header",
+          "value": "My Value"
         }
       ]
+    }
+  ],
+  "functions": {
+    "api/**/*.ts": {
+      "runtime": "nodejs20.x"
+    }
+  }
 }