IR: Stop printing 'metadata' in Metadata::print()

Stop printing `metadata` in `Metadata::print()` and
`Metadata::printAsOperand()`.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224327 91177308-0d34-0410-b5e6-96231b3b80d8
Remove 'metadata' from comments

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224328 91177308-0d34-0410-b5e6-96231b3b80d8