[ConstantFolding] Drop misleading comment (NFC)

As pointed out by Philip, this part of the comment is misleading,
as it describes undef rather than poison behavior. Just mentioning
poison should be sufficient.

llvm/include/llvm/Analysis/ConstantFolding.h

@@ -129,8 +129,7 @@ Constant *ConstantFoldShuffleVectorInstruction(Constant *V1, Constant *V2,
                                                ArrayRef<int> Mask);
 
 /// Extract value of C at the given Offset reinterpreted as Ty. If bits past
-/// the end of C are accessed, they are assumed to be poison and may take any
-/// value.
+/// the end of C are accessed, they are assumed to be poison.
 Constant *ConstantFoldLoadFromConst(Constant *C, Type *Ty, const APInt &Offset,
                                     const DataLayout &DL);