[NFC] Remove overconfident assert from IRCE

This patch removes assert that SCEV is able to prove that a value is
non-negative. In fact, SCEV can sometimes be unable to do this because
its cache does not update properly. This assert will be returned once this
problem is resolved.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323309 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed