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

js/js.translator/testData/box/multiModule/privateInterfaceMethodInheritance.kt

@@ -1,4 +1,3 @@
-// IGNORE_FIR
 // EXPECTED_REACHABLE_NODES: 1280
 // KJS_WITH_FULL_RUNTIME
 // MODULE: lib
@@ -23,4 +22,4 @@ import lib.AProxy
 // Important bit: don't inherit A directly
 class B : AProxy()
 
-fun box(): String = B().bar()
+fun box(): String = B().bar()