cleanup: upstream dropped amx-transpose functionality

[durin42]

See also LLVM change 5322fb626820. Looks like this was just removed entirely.
It seems a little bad to just drop it, but I don't see an easy way to conditionalize
this and if it's really just Gone and we marked it as unstable (which it looks like
we did?) I guess we should just dump it.

@rustbot label llvm-main

[rustbot]

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[ilovepi]

#126622 was tracking the support. The change looks sane to me given Intel is dropping it everywhere. It'd great to get this or another workaround landed soon, since its blocking Fuchsia from getting new toolchain candidates, and I imagine Chrome and Android will hit this soon as well.

[workingjubilee]

lgtm.

@bors r+

[bors]

📌 Commit efb9a41 has been approved by workingjubilee

It is now in the queue for this repository.