[NewGVN] Get rid of an assertion.

This was here because we don't want to switch leaders too much,
in order to avoid fixpoint(ing) issue, but it's not sure if it
matters in practice.

A first step towards fixing PR32897.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303473 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed