C++: Address review comment

Author: jketema

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll

@@ -49,10 +49,7 @@ class Node0Impl extends TIRDataFlowNode0 {
   Instruction asInstruction() { result = this.(InstructionNode0).getInstruction() }
 
   /** Gets the operands corresponding to this node, if any. */
-  Operand asOperand() {
-    result = this.(MultipleUseOperandNode0).getOperand() or
-    result = this.(SingleUseOperandNode0).getOperand()
-  }
+  Operand asOperand() { result = this.(OperandNode0).getOperand() }
 
   /** INTERNAL: Do not use. */
   Location getLocationImpl() {