Update data/tutorials/ds_02_set.md

Author: christinerose

data/tutorials/ds_02_set.md

@@ -15,7 +15,7 @@ a set; instead, you must first specify what type of elements your set will
 contain.
 
 The `Set` functor provides a function `Make` which accepts a module as a
-parameter, and returns a new module representing a set whose elements have
+parameter and returns a new module representing a set whose elements have
 the type that you passed in. For example, if you want to work with sets of
 strings, you can invoke `Set.Make(String)` which will return you a new module
 which you can assign the name `SS` (short for "String Set"). Note: Be sure to