Wrap words at 80 characters

Author: corincerami

src/doc/trpl/lifetimes.md

@@ -70,7 +70,8 @@ fn bar<'a>(x: &'a i32) {
 ```
 
 The `'a` reads ‘the lifetime a’. Technically, every reference has some lifetime
-associated with it, but the compiler lets you elide (i.e. omit, see ["Lifetime Elision"][lifetime-elision] below) them in common cases.
+associated with it, but the compiler lets you elide (i.e. omit, see
+["Lifetime Elision"][lifetime-elision] below) them in common cases.
 Before we get to that, though, let’s break the explicit example down:
 
 [lifetime-elision]: #user-content-lifetime-elision