fix typo in 7.14 sync (#278)

Author: xiorcale

book/src/07_threads/14_sync.md

@@ -5,7 +5,7 @@ Before we wrap up this chapter, let's talk about another key trait in Rust's sta
 `Sync` is an auto trait, just like `Send`.\
 It is automatically implemented by all types that can be safely **shared** between threads.
 
-In order words: `T` is Sync if `&T` is `Send`.
+In other words: `T` is Sync if `&T` is `Send`.
 
 ## `T: Sync` doesn't imply `T: Send`