Reuse BuildAgent license after moving agent from linux to windows

Hello,

we're running TeamCity Enterprise with a limit of 3 BuildAgents. We had three agents running on linux.
Now we want to move one of the BuildAgents from a linux to a windows host.

So I've installed an agent on the windows host and I can see it in the TeamCity Admin UI as "unauthorized". But because of the license limit I'm not able to authorize this agent.
I stopped one of the linux agents, but how can I remove this agent from TC to free it's license? I found the post in https://devnet.jetbrains.com/message/5195667#5195667 saying that agents disappear after a week, but we do not have the time to wait for e week.

Thanks,
Thorsten