Rollup merge of rust-lang#28210 - tshepang:typo, r=steveklabnik

Author: steveklabnik

src/doc/trpl/choosing-your-guarantees.md

@@ -243,7 +243,7 @@ Many of the types above cannot be used in a threadsafe manner. Particularly, `Rc
 `RefCell<T>`, which both use non-atomic reference counts (_atomic_ reference counts are those which
 can be incremented from multiple threads without causing a data race), cannot be used this way. This
 makes them cheaper to use, but we need thread safe versions of these too. They exist, in the form of
-`Arc<T>` and `Mutex<T>`/`RWLock<T>`
+`Arc<T>` and `Mutex<T>`/`RwLock<T>`
 
 Note that the non-threadsafe types _cannot_ be sent between threads, and this is checked at compile
 time.