Clean up HashSet Examples

src/libstd/collections/hash/set.rs

@@ -66,17 +66,17 @@
 /// books.insert("The Great Gatsby");
 ///
 /// // Check for a specific one.
-/// if !books.contains(&("The Winds of Winter")) {
+/// if !books.contains("The Winds of Winter") {
 ///     println!("We have {} books, but The Winds of Winter ain't one.",
 ///              books.len());
 /// }
 ///
 /// // Remove a book.
-/// books.remove(&"The Odyssey");
+/// books.remove("The Odyssey");
 ///
 /// // Iterate over everything.
-/// for book in books.iter() {
-///     println!("{}", *book);
+/// for book in &books {
+///     println!("{}", book);
 /// }
 /// ```
 ///
@@ -100,7 +100,7 @@
 /// vikings.insert(Viking { name: "Harald", power: 8 });
 ///
 /// // Use derived implementation to print the vikings.
-/// for x in vikings.iter() {
+/// for x in &vikings {
 ///     println!("{:?}", x);
 /// }
 /// ```