There is no need to list sanitizers in both "UndefinedTrap" and
"Undefined" groups - it turns out using one group in a defintion
of another group "just works".

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@231040 91177308-0d34-0410-b5e6-96231b3b80d8