[CMake] Simplify cmake config of gdml.

Remove link to cuda library.

In !866 (closed), I proposed an update to the CMake config. After @bmorgan managed to cherry pick most of the commits, this is the only one that's left that remained after rebasing the original branch. It looks like the link to the cuda lib is not needed, any more; at least it worked locally.

Let's see what the CI says.