chore: Fix hardcoded endpoint domain in test template (#3663)

Author: samson-keung

integration/resources/templates/single/basic_api_with_mode.yaml

@@ -31,6 +31,6 @@ Resources:
 
 Outputs:
   ApiEndpoint:
-    Value: !Sub "https://${MyApi}.execute-api.${AWS::Region}.amazonaws.com/MyNewStageName"
+    Value: !Sub "https://${MyApi}.execute-api.${AWS::Region}.${AWS::URLSuffix}/MyNewStageName"
 Metadata:
   SamTransformTest: true