JS: move expressions test to box tests

js/js.translator/testData/box/expression/when/whenWithIfConditionAndOnlyElse.kt

@@ -0,0 +1,15 @@
+package foo
+
+var global = ""
+
+fun <T> bar(a: T, i: Int): T {
+    global += "$i"
+    return a
+}
+
+fun box(): String {
+    val x = 3
+    when(if (x == 4) return bar("fail1", 1) else 4) {
+        else -> return bar("OK", 2)
+    }
+}