[K/N] Enable callbackOnSeparateThread test since KT-44283 is fixed

kotlin-native/backend.native/tests/interop/threadStates/threadStates.kt

@@ -13,9 +13,7 @@ fun main() {
     callback()
     nestedCalls()
     directStaticCFunctionCall()
-    // TODO: Support runtime initialization for callbacks
-    //       see: https://youtrack.jetbrains.com/issue/KT-44283
-    // callbackOnSeparateThread()
+    callbackOnSeparateThread()
 }
 
 fun assertRunnableThreadState() {