Updated AVL Tree to Swift 4.2

Author: karolms

AVL Tree/AVLTree.playground/Contents.swift

@@ -1,9 +1,5 @@
 //: Playground - noun: a place where people can play
 
-// last checked with Xcode 9.0b4
-#if swift(>=4.0)
-print("Hello, Swift 4!")
-#endif
 
 let tree = AVLTree<Int, String>()