Fix typo in dummy app

Author: pascalwengerter

spec/dummy/app/controllers/my_app_controller.rb

@@ -55,7 +55,7 @@ def delete_dummy_model
     else
       render json: {
         errors: @dummy_model.errors,
-        message: "Test Model could not be saved!"
+        message: "Test Model could not be deleted!"
         }, status: :unproccessable_entity
     end