Fix package name

Author: qwwdfsad

core/kotlinx-coroutines-core/test/channels/InvokeOnCloseStressTest.kt

@@ -2,7 +2,7 @@
  * Copyright 2016-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
-package channels
+package kotlinx.coroutines.experimental.channels
 
 import kotlinx.coroutines.experimental.*
 import kotlinx.coroutines.experimental.channels.*