JS: move more test to box tests

js/js.translator/testData/box/operatorOverloading/usingModInCaseModAssignNotAvailable.kt

@@ -0,0 +1,15 @@
+package foo
+
+class A() {
+    var p = "yeah"
+    operator fun mod(other: A): A {
+        return A();
+    }
+}
+
+fun box(): String {
+    var c = A()
+    val d = c;
+    c %= A();
+    return if ((c != d) && (c.p == "yeah")) "OK" else "fail"
+}