r226504 added `TempMDNodeDeleter` to help with `std::unique_ptr<>`-izing
the `MDNode::getTemporary()` interface. It doesn't need to be
templated, though.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226509 91177308-0d34-0410-b5e6-96231b3b80d8