JS: move expressions test to box tests

js/js.translator/testData/box/expression/misc/classWithoutPackage.kt

@@ -0,0 +1,11 @@
+class A(var a: Int) {
+    init {
+        a = 3
+    }
+}
+
+fun box(): String {
+    val result = A(1).a
+    if (result != 3) return "fail: $result"
+    return "OK"
+}