updated LinkedList.playground to swift 4.2

Author: varun989

Linked List/LinkedList.playground/Contents.swift

@@ -3,10 +3,6 @@
 // For best results, don't forget to select "Show Rendered Markup" from XCode's "Editor" menu
 
 //: Linked List Class Declaration:
-// last checked with Xcode 9.0b4
-#if swift(>=4.0)
-print("Hello, Swift 4!")
-#endif
 
 public final class LinkedList<T> {
 

Linked List/LinkedList.playground/contents.xcplayground

@@ -1,4 +1,4 @@
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<playground version='5.0' target-platform='osx' display-mode='rendered'>
+<playground version='5.0' target-platform='osx' display-mode='rendered' last-migration='1000'>
     <timeline fileName='timeline.xctimeline'/>
 </playground>