My 2 year old Damson tree seems sturdy but grows from 2 trunks ( split at the base) Should I cut one off

Depends if this is a grafted or seed grown damson, and whether the trunks are coming from below or above the graft.
If not grafted, I would leave it alone with the 'bush' shape of two trunks. If you don't want to, choose the weakest and remove that while the tree is still in leaf. Don't prune it in the winter because of the danger of silver leaf.