fix nll test stderr

Author: ChrisPardy

src/test/ui/regions/regions-addr-of-upvar-self.nll.stderr

@@ -23,7 +23,7 @@ error[E0597]: `self` does not live long enough
 LL |         let _f = || {
    |                  -- value captured here
 LL |             let p: &'static mut usize = &mut self.food;
-   |                    ------------------        ^^^^ borrowed value does not live long enough
+   |                    ------------------        ^^^^^^^^^ borrowed value does not live long enough
    |                    |
    |                    type annotation requires that `self` is borrowed for `'static`
 ...