Got you @Rene_Wynands!
As it stands, if you’re the last member of a team, you can delete it, but you can’t leave it as a team can’t leave without at least one user.
In your specific case, I’d recommend moving it (using drag and drop) to the very bottom of your sidebar to avoid seeing it too much, and if you haven’t yet, make sure to cast your vote on this other thread from our forum Option To Archive Teams!