[llvm] Revert "[RegAlloc] Strengthen asserts in LiveRangeEdit::scanRemattable [nfc]" (PR #160897)

[Philip Reames via llvm-commits]

preames wrote:

> > Reverts #160765. Failures on buildbot indicate second assertion does not in fact hold.
> 
> Include reduced sample?

Don't yet have one.  It looks like a stage2 compile failed, but only on the riscv bots so far, which is weird.  I do plan to try and extract a test case here, but wanted to get the bots clean first.

https://github.com/llvm/llvm-project/pull/160897