[DAG] Fix incorrect doxygen comment for isZeroOrZeroSplat (NFC) (#163527)

Author: hazzlim

llvm/include/llvm/CodeGen/SelectionDAGNodes.h

@@ -1950,7 +1950,7 @@ LLVM_ABI bool isOnesOrOnesSplat(SDValue N, bool AllowUndefs = false);
 
 /// Return true if the value is a constant 0 integer or a splatted vector of a
 /// constant 0 integer (with no undefs).
-/// Does not permit build vector implicit truncation.
+/// Build vector implicit truncation is allowed.
 LLVM_ABI bool isZeroOrZeroSplat(SDValue N, bool AllowUndefs = false);
 
 /// Return true if \p V is either a integer or FP constant.