fix: Correct Amazon Q endpoint URL path

Revert the Amazon Q endpoint path to root '/' instead of '/generateAssistantResponse'.

The '/generateAssistantResponse' path is only for CodeWhisperer endpoint with
'GenerateAssistantResponse' target. Amazon Q endpoint uses 'SendMessage' target
which requires the root path.

Thanks to @gemini-code-assist for catching this copy-paste error.

internal/runtime/executor/kiro_executor.go

@@ -364,7 +364,7 @@ func buildKiroEndpointConfigs(region string) []kiroEndpointConfig {
 			Name:      "CodeWhisperer",
 		},
 		{
-			URL:       fmt.Sprintf("https://q.%s.amazonaws.com/generateAssistantResponse", region),
+			URL:       fmt.Sprintf("https://q.%s.amazonaws.com/", region),
 			Origin:    "CLI",
 			AmzTarget: "AmazonQDeveloperStreamingService.SendMessage",
 			Name:      "AmazonQ",