Simplify mcp.run example by removing json_response

Removed the json_response argument from mcp.run in the example.

Author: DevenWen

README.md

@@ -177,7 +177,7 @@ def greet_user(name: str, style: str = "friendly") -> str:
 
 # Run with streamable HTTP transport
 if __name__ == "__main__":
-    mcp.run(transport="streamable-http", json_response=True)
+    mcp.run(transport="streamable-http")
 ```
 
 _Full example: [examples/snippets/servers/mcpserver_quickstart.py](https://github.com/modelcontextprotocol/python-sdk/blob/main/examples/snippets/servers/mcpserver_quickstart.py)_