[JS] Remove non-functional IGNORE_FIR directive in js box tests

js/js.translator/testData/box/esModules/crossModuleRefPerModule/objectIsObject.kt

@@ -1,4 +1,3 @@
-// IGNORE_FIR
 // DONT_TARGET_EXACT_BACKEND: JS
 // ES_MODULES
 // SPLIT_PER_MODULE
@@ -21,4 +20,4 @@ fun box(): String {
     if (!(o is O)) return "fail2"
 
     return "OK"
-}
+}