sort: delete now-duplicate example, fix build

R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/7220075

src/pkg/sort/example_reverse_test.go

-// Copyright 2011 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package sort_test
-
-import (
-	"fmt"
-	"sort"
-)
-
-// Reverse embeds a sort.Interface value and implements a reverse sort over
-// that value.
-type Reverse struct {
-	// This embedded Interface permits Reverse to use the methods of
-	// another Interface implementation.
-	sort.Interface
-}
-
-// Less returns the opposite of the embedded implementation's Less method.
-func (r Reverse) Less(i, j int) bool {
-	return r.Interface.Less(j, i)
-}
-
-func ExampleInterface_reverse() {
-	s := []int{5, 2, 6, 3, 1, 4} // unsorted
-	sort.Sort(Reverse{sort.IntSlice(s)})
-	fmt.Println(s)
-	// Output: [6 5 4 3 2 1]
-}