repalce functions with builds in vercel.json

Author: tonyqiu123

backend/vercel.json

@@ -1,20 +1,21 @@
 {
   "buildCommand": "bash vercel-build.sh",
-  "functions": {
-    "api/wsgi.py": {
-      "maxDuration": 30
+  "builds": [
+    {
+      "src": "api/wsgi.py",
+      "use": "@vercel/python",
+      "config": {
+        "maxLambdaSize": "15mb"
+      }
     }
-  },
+  ],
   "routes": [
     {
       "src": "/(.*)",
       "dest": "api/wsgi.py"
     }
   ],
-  "build": {
-    "env": {
-      "PYTHONPATH": "."
-    }
-  },
-  "outputDirectory": "."
+  "env": {
+    "PYTHONPATH": "."
+  }
 }