IR: Remove MDTupleTypedArrayWrapper::operator MDTuple*()

Remove `MDTupleTypedArrayWrapper::operator MDTuple*()`, since it causes
ambiguity (at least in some [1] compilers [2]) when using indexes to
`MDTupleTypedArrayWrapper::operator[](unsigned)` that are convertible to
(but not the same as) `unsigned`.

[1]: http://lab.llvm.org:8011/builders/sanitizer-windows/builds/2308
[2]: http://lab.llvm.org:8011/builders/clang-cmake-mips/builds/4442

llvm-svn: 234326
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 6cb3c72..ba50ecb 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -110,6 +110,10 @@
     OS << '\n';
   }
 
+  template <class T> void Write(const MDTupleTypedArrayWrapper<T> &MD) {
+    Write(MD.get());
+  }
+
   void Write(const NamedMDNode *NMD) {
     if (!NMD)
       return;