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

[Matt Arsenault via llvm-commits]

arsenm wrote:

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

Include reduced sample? 

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