[llvm] [IR] Avoid visited set for simple isScalableTy queries (NFC) (PR #221743)

[Cullen Rhodes via llvm-commits]

c-rhodes wrote:

I'm not actually sure the visited set is necessary anymore now types can't be recursive (#114799), it looks like it can be removed, might be better to do that as a follow up

https://github.com/llvm/llvm-project/pull/221743