Remove GPU constraint

This MR removes the GPU constraint as comment here https://gitlab.aei.uni-hannover.de/cw-group/lalsuite/merge_requests/54#note_12699 . I also remove it in the example.

/cc @bema @ReinhardPrix

seems fine with me, but I cannot merge. You might want to assign this to Bernd for additional vetting & merging.

I am not allow to assign this to Bernd , but I will request access to this project and than I can do it

mentioned in commit 0edfa5d2

merged

mentioned in issue #3