[llvm] Remove iOS 5 check for tailcalls on ARM (PR #133354)

[Reid Kleckner via llvm-commits]

rnk wrote:

I think this makes sense. I feel like our approach is that LLVM should support *targeting* old hardware, but we don't necessarily support integrating with old tools. Our toolchain support policy requires people to upgrade host toolchains frequently.

So, under that reasoning, I think we can approve this. @jroelofs already did, so I'll merge it.

https://github.com/llvm/llvm-project/pull/133354