IR: Fix comment spelling, NFC

llvm-svn: 226058

Author: dexonsmith

llvm/include/llvm/IR/Metadata.h

@@ -894,7 +894,7 @@ class MDNodeFwdDecl : public MDNode, ReplaceableMetadataImpl {
 public:
   ~MDNodeFwdDecl() { dropAllReferences(); }
 
-  // MSVC doesn't seem to see the alternaive: "using MDNode::operator delete".
+  // MSVC doesn't see the alternative: "using MDNode::operator delete".
   void operator delete(void *Mem) { MDNode::operator delete(Mem); }
 
   static MDNodeFwdDecl *get(LLVMContext &Context, ArrayRef<Metadata *> MDs) {