JS: move expressions test to box tests

js/js.translator/testData/box/expression/stringClass/stringInTemplate.kt

@@ -0,0 +1,10 @@
+// CHECK_NOT_CALLED_IN_SCOPE: scope=box function=toString
+
+package foo
+
+fun box(): String {
+    var name = "Hello"
+    assertEquals("oHelloo", "o${name}o")
+    return "OK";
+}
+