Fix moveSubranges documentation issue

Author: Kyle-Ye

stdlib/public/core/MutableCollection.swift

@@ -379,8 +379,8 @@ extension MutableCollection {
   ///     var letters = Array("ABCdeFGhijkLMNOp")
   ///     let uppercaseRanges = letters.indices(where: { $0.isUppercase })
   ///     let rangeOfUppercase = letters.moveSubranges(uppercaseRanges, to: 10)
-  ///     // String(letters) == "dehiABCFGLMNOjkp"
-  ///     // rangeOfUppercase == 4..<13
+  ///     // String(letters) == "dehijABCFGLMNOkp"
+  ///     // rangeOfUppercase == 5..<14
   ///
   /// - Parameters:
   ///   - subranges: The subranges of the elements to move.