Remove HEAD operation status code warning (Azure#1265)

- HEAD methods now only LogInfo instead of LogWarning when
   pointing out that you might be mistaken if you're missing
   two status codes.

src/core/AutoRest.Extensions.Azure/AzureExtensions.cs

@@ -111,7 +111,7 @@ public static void UpdateHeadMethods(ServiceClient serviceClient)
                 }
                 else
                 {
-                    Logger.LogWarning(string.Format(CultureInfo.InvariantCulture, Resources.HeadMethodPossibleIncorrectSpecification, method.Name));
+                    Logger.LogInfo(string.Format(CultureInfo.InvariantCulture, Resources.HeadMethodPossibleIncorrectSpecification, method.Name));
                 }
             }
         }