Minor typo correction

Author: voidance

_tour/traits.md

@@ -62,7 +62,7 @@ iterator.next()  // prints 1
 This `IntIterator` class takes a parameter `to` as an upper bound. It `extends Iterator[Int]` which means that the `next` method must return an Int.
 
 ## Subtyping
-Subtypes of traits can be used where a the trait is required.
+Subtypes of traits can be used where the trait is required.
 ```tut
 import scala.collection.mutable.ArrayBuffer