Correct sorting example for Ordering in scaladoc

	Below code snippet,
    Sorting.quickSort(pairs)(Ordering.by[(String, Int, Int), Int](_._2)

    should be
    Sorting.quickSort(pairs)(Ordering.by[(String, Int, Int), Int](_._2))
Merge pull request #2303 from starblood/gyuhang/libdoc

Correct sorting example for Ordering in scaladoc