[llvm] Revert "[GlobalISel] Add support for lowering byref attribute" (PR #96784)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm requested changes to this pull request.

Revert description gives no rationale. This isn't meaningfully testable without a target in need so -1 

https://github.com/llvm/llvm-project/pull/96784