language tour: tweak wording in tuples section

references scala#1728

Author: SethTisue

_tour/tuples.md

@@ -12,7 +12,7 @@ redirect_from: "/tutorials/tour/tuples.html"
 ---
 
 In Scala, a tuple is a value that contains a fixed number of elements, each
-with a distinct type.  Tuples are immutable.
+with its own type.  Tuples are immutable.
 
 Tuples are especially handy for returning multiple values from a method.