Revert "[GVNHoist] Re-enable GVNHoist by default"

This reverts commit r338240 because it was causing OOMs on the UBSan
buildbot when building clang/lib/Sema/SemaChecking.cpp

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@338297 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed