Corrects variable name in max functions to better reflect usage

The variable smallestThree should really be named largestThree. Looks
like this was originally a copy paste error from the min documentation.

Sources/Algorithms/MinMax.swift

@@ -125,7 +125,7 @@ extension Sequence {
   /// largest values:
   ///
   ///     let numbers = [7, 1, 6, 2, 8, 3, 9]
-  ///     let smallestThree = numbers.max(count: 3, sortedBy: <)
+  ///     let largestThree = numbers.max(count: 3, sortedBy: <)
   ///     // [7, 8, 9]
   ///
   /// If you need to sort a sequence but only need to access its largest
@@ -197,7 +197,7 @@ extension Sequence where Element: Comparable {
   /// largest values:
   ///
   ///     let numbers = [7, 1, 6, 2, 8, 3, 9]
-  ///     let smallestThree = numbers.max(count: 3)
+  ///     let largestThree = numbers.max(count: 3)
   ///     // [7, 8, 9]
   ///
   /// If you need to sort a sequence but only need to access its largest
@@ -280,7 +280,7 @@ extension Collection {
   /// largest values:
   ///
   ///     let numbers = [7, 1, 6, 2, 8, 3, 9]
-  ///     let smallestThree = numbers.max(count: 3, sortedBy: <)
+  ///     let largestThree = numbers.max(count: 3, sortedBy: <)
   ///     // [7, 8, 9]
   ///
   /// If you need to sort a collection but only need to access its largest