[minor] fix import statement position in testdata

the import statement is (should be) ignored before FILE directive

js/js.translator/testData/box/reflection/kClassWithJsCall.kt

@@ -1,6 +1,6 @@
+// FILE: main.kt
 import kotlin.reflect.KClass
 
-// FILE: main.kt
 external abstract open class A(
     o: String
 ) {