Fix MCP tests to use conversation instead of previous_response_id (#44270)

Both test_agent_mcp_basic and test_agent_mcp_with_project_connection were creating conversations but incorrectly switching to previous_response_id for follow-up calls. This fix ensures they consistently use conversation.id.

Author: paulbatum

sdk/ai/azure-ai-projects/tests/agents/tools/test_agent_mcp.py

@@ -128,8 +128,8 @@ def test_agent_mcp_basic(self, **kwargs):
             print("\nSending approval response to continue agent execution...")
 
             response = openai_client.responses.create(
+                conversation=conversation.id,
                 input=input_list,
-                previous_response_id=response.id,
                 extra_body={"agent": {"name": agent.name, "type": "agent_reference"}},
             )
 
@@ -275,8 +275,8 @@ def test_agent_mcp_with_project_connection(self, **kwargs):
             print("\nSending approval response to continue agent execution...")
 
             response = openai_client.responses.create(
+                conversation=conversation.id,
                 input=input_list,
-                previous_response_id=response.id,
                 extra_body={"agent": {"name": agent.name, "type": "agent_reference"}},
             )