Make tests about mod and varargs valid for 1.3 version

compiler/testData/codegen/box/operatorConventions/assignmentOperations.kt

@@ -7,7 +7,7 @@ operator fun A.plusAssign(y: Int) { x += y }
 operator fun A.minusAssign(y: Int) { x -= y }
 operator fun A.timesAssign(y: Int) { x *= y }
 operator fun A.divAssign(y: Int) { x /= y }
-operator fun A.modAssign(y: Int) { x %= y }
+operator fun A.remAssign(y: Int) { x %= y }
 
 fun box(): String {
   val original = A()

compiler/testData/codegen/box/operatorConventions/remAssignmentOperation.kt

@@ -1,3 +1,5 @@
+// !LANGUAGE: -ProhibitOperatorMod
+
 class A() {
     var x = 5
 }

compiler/testData/codegen/box/operatorConventions/remOverModOperation.kt

@@ -1,3 +1,5 @@
+// !LANGUAGE: -ProhibitOperatorMod
+
 class A() {
     var x = 5