Fix tiny spelling mistake in book

Changed datastructure to data structure

src/doc/book/borrow-and-asref.md

@@ -8,7 +8,7 @@ different. Here’s a quick refresher on what these two traits mean.
 
 # Borrow
 
-The `Borrow` trait is used when you’re writing a datastructure, and you want to
+The `Borrow` trait is used when you’re writing a data structure, and you want to
 use either an owned or borrowed type as synonymous for some purpose.
 
 For example, [`HashMap`][hashmap] has a [`get` method][get] which uses `Borrow`:
@@ -86,7 +86,7 @@ We can see how they’re kind of the same: they both deal with owned and borrowe
 versions of some type. However, they’re a bit different.
 
 Choose `Borrow` when you want to abstract over different kinds of borrowing, or
-when you’re building a datastructure that treats owned and borrowed values in
+when you’re building a data structure that treats owned and borrowed values in
 equivalent ways, such as hashing and comparison.
 
 Choose `AsRef` when you want to convert something to a reference directly, and