Fix url in azure-openai-responses-agent.md (#745)

https://github.com/MicrosoftDocs/semantic-kernel-pr/pull/738/files/44201cfde92d3551272bb2c7f37993fbaad42d71#r2469981625

Author: jozkee

agent-framework/user-guide/agents/agent-types/azure-openai-responses-agent.md

@@ -37,7 +37,7 @@ using Microsoft.Agents.AI;
 using OpenAI;
 
 AzureOpenAIClient client = new AzureOpenAIClient(
-    new Uri("https://<myresource>.openai.azure.com/openai/v1/"),
+    new Uri("https://<myresource>.openai.azure.com/"),
     new AzureCliCredential());
 ```