[Docs] [Serve] remove unused json resolver (ray-project#33104)

Removes unused lines in serve example

Why?
In this example, there's already an imported json resolver from ray.serve.http_adapters import json_request such that these lines are unused.

doc/source/serve/doc_code/production_fruit_example.py

@@ -9,8 +9,7 @@
 from ray.serve.http_adapters import json_request
 
 # These imports are used only for type hints:
-from typing import Dict, List
-from starlette.requests import Request
+from typing import Dict
 
 
 @serve.deployment(num_replicas=2)
@@ -88,10 +87,6 @@ def check_price(self, amount: float) -> float:
         return self.price * amount
 
 
-async def json_resolver(request: Request) -> List:
-    return await request.json()
-
-
 with InputNode() as query:
     fruit, amount = query[0], query[1]