Make tests about mod and varargs valid for 1.3 version

compiler/testData/codegen/box/vararg/singleAssignmentToVarargsInFunction.kt

@@ -0,0 +1,34 @@
+// !LANGUAGE: -ProhibitAssigningSingleElementsToVarargsInNamedForm
+// IGNORE_BACKEND: JS_IR
+
+fun box(): String {
+    if (test1(p = 1) != "1") return "fail 1"
+    if (test2(p = "1") != "1") return "fail 2"
+    if (test3(p = "1") != "1") return "fail 3"
+
+    return "OK"
+}
+
+fun test1(vararg p: Int): String {
+    var result = ""
+    for (i in p) {
+        result += i
+    }
+    return result
+}
+
+fun test2(vararg p: String): String {
+    var result = ""
+    for (i in p) {
+        result += i
+    }
+    return result
+}
+
+fun <T> test3(vararg p: T): String {
+    var result = ""
+    for (i in p) {
+        result += i
+    }
+    return result
+}