[llvm] [MemProf] Remove empty edges once after cloning (PR #85320)

[Teresa Johnson via llvm-commits]

teresajohnson wrote:

> Does it make sense to add a separate test for this or is it covered in upcoming changes?

This is essentially an NFC change (I thought about adding NFC to it but decided not since it changes enough about the internal ordering of the graph transformation, although it should have no impact on anything user-visible).

https://github.com/llvm/llvm-project/pull/85320