reword to avoid using a term used in a confusing manner, "error annotations"

Author: tshepang

src/doc/rustc-dev-guide/src/tests/ui.md

@@ -309,8 +309,9 @@ fn main((ؼ
 
 Use `//~?` to match an error without line information.
 `//~?` is precise and will not match errors if their line information is available.
-For tests wishing to match against compiler diagnostics, error annotations should
-be preferred over //@ error-pattern, //@ error-pattern is imprecise and non-exhaustive.
+It should be preferred over `//@ error-pattern`
+for tests wishing to match against compiler diagnostics,
+due to `//@ error-pattern` being imprecise and non-exhaustive.
 
 ```rust,ignore
 //@ compile-flags: --print yyyy