Utils: MDNode => UniquableMDNode, NFC

Although this makes the `cast<>` assert more often, the
`assert(Node->isResolved())` on the following line would assert in all
those cases.  So, no functionality change here.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225903 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed