Auto merge of #26247 - steveklabnik:remove_4120, r=alexcrichton

This test originated from an ICE in Rust 0.4:
https://github.com/rust-lang/rust/commit/373504a7ac6801293ae65316625ace667842f5b8#diff-214656000770dff71c8165d051c3f027

it was ignored one day later:
https://github.com/rust-lang/rust/commit/1fa2b9980fabff3227d5e5915d1180a0f6922d37#diff-214656000770dff71c8165d051c3f027

and then never enabled again. I think we're safe without it.