There is no license deactivation process. Just install Lightroom on your next computer.
But don't I have limited times I can activate the license key (3 times on 3 different computers)?
You seem to be comparing Lightroom to Photoshop.
There is no global limit on the number of times you can install and use the license for Lightroom. The limit is that you can only have it installed and using the license on two computers at any one time (and the two computers can't be both using Lightroom at the same time and the two computers must be used for your own personal use).
Ok, thank you very much. I'll try to install it on a new pc and just disintall it on the old one.