Back in April, in one of my posts (read it here) I explained that it was no more necessary to include the "Xamarin License step" when building Xamarin solutions using the Hosted Agents.
Starting from now, it is no more necessary to include this step for every Xamarin builds, for both Hosted and personal agents.
Indeed, as reported on the new Visual Studio Team Service update:
The Xamarin License step is no longer necessary and has been removed from the build templates shipped with VSTS and TFS 15. As part of this effort we will also deprecate the task. All build definitions that use this task should be updated to remove it in order to prevent any disruption when the task is finally removed.
Have good builds ;)