Auto merge of #99056 - lcnr:higher_ranked_sub, r=oli-obk

Auto merge of #99056 - lcnr:higher_ranked_sub, r=oli-obk

don't use `commit_if_ok` during `higher_ranked_sub`

This snapshot doesn't really do anything useful for us, especially once we deal with placeholder outlive bounds during trait solving.

I guess that currently the idea is that `higher_ranked_sub` could cause a later `leak_check` to fail even if the combine operation isn't actually relevant. But really, using combine outside of snapshot and ignoring its result is wrong anyways, as it can constrain inference variables.

r? rust-lang/types