Update Sorted Set to Swift 4.2

Author: pchelnikov

Sorted Set/SortedSet.playground/Pages/Example 1.xcplaygroundpage/Contents.swift

@@ -1,8 +1,3 @@
-// last checked with Xcode 9.0b4
-#if swift(>=4.0)
-print("Hello, Swift 4!")
-#endif
-
 //: # Example 1 with type Int
 
 var mySet = SortedSet<Int>()