don't deep copy program (#4575)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/4575

Lowering LLava Model to delegate complains at this point because of the deep copy. I remove it here.

If there is nothing is happening to this EP (no partitioner to delegate) then there is no need to deep copy in the first place

Differential Revision: D60156120

fbshipit-source-id: fa5827456a5225e75c26644537f7ca263e675fa8