gn: Fix integer subtraction.

tools/gn/operators.cc

Index: tools/gn/operators.cc
diff --git a/tools/gn/operators.cc b/tools/gn/operators.cc
index 72b2dd18ce63ade447721cbc8a199c5b24699b9b..350fef4286b014f8f949c55934e3f39f16056055 100644
--- a/tools/gn/operators.cc
+++ b/tools/gn/operators.cc
@@ -419,7 +419,7 @@ Value ExecuteMinus(const BinaryOpNode* op_node,
                    const Value& right,
                    Err* err) {
   // Left-hand-side int. The only thing to do is subtract another int.
-  if (left.type() == Value::INTEGER && right.type() != Value::INTEGER) {
+  if (left.type() == Value::INTEGER && right.type() == Value::INTEGER) {
     // Int - int -> subtraction.
     return Value(op_node, left.int_value() - right.int_value());
   }