Rollup merge of #91367 - FabianWolff:issue-91334-ice, r=nagisa

Fix ICE in `check_must_not_suspend_ty()`

Fixes #91334. I have also used `TyS::tuple_fields()` (instead of the `SubstsRef` directly) to get the tuple fields, because that's what [the documentation](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/enum.TyKind.html#variant.Tuple) says, although it doesn't seem to make a difference in practice (this is not what fixed the ICE).