Converting two lights from one switch to one light from one switch?
Look in the holes the wires come from, one of the has 2 sets of wires coming in, one set to the switch and one to the other side.

Disconnect the one to the other side and cap it off. Then just use the wire from the switch to power the new bar. The hole on the other side you can cap of the wires and leave a cover plate in place.

It is possible that 2 sets of wires leave from the switch to both sides, then you disconnect one set and use the other to power the bar (again capping off the unused wires).

Instead of capping off the wires you would remove them entirely leaving just the set to power the bar and patch the holes in the wall; though that usually requires access to the space behind it.