Use a more common word than "elide", e.g. omit

Author: Chris C Cerami

src/doc/trpl/lifetimes.md

@@ -70,7 +70,7 @@ 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 them in common cases.
+associated with it, but the compiler lets you omit them in common cases.
 Before we get to that, though, let’s break the explicit example down:
 
 ```rust,ignore