fix unit tests

Author: Guanqun Lu

src/test/ui/suggestions/remove-as_str.stderr

@@ -2,25 +2,25 @@ error[E0599]: no method named `as_str` found for type `&str` in the current scop
   --> $DIR/remove-as_str.rs:2:7
    |
 LL |     s.as_str();
-   |       ^^^^^^ help: try removing `as_str`
+   |       ^^^^^^ try removing `as_str`
 
 error[E0599]: no method named `as_str` found for type `&'a str` in the current scope
   --> $DIR/remove-as_str.rs:7:7
    |
 LL |     s.as_str();
-   |       ^^^^^^ help: try removing `as_str`
+   |       ^^^^^^ try removing `as_str`
 
 error[E0599]: no method named `as_str` found for type `&mut str` in the current scope
   --> $DIR/remove-as_str.rs:12:7
    |
 LL |     s.as_str();
-   |       ^^^^^^ help: try removing `as_str`
+   |       ^^^^^^ try removing `as_str`
 
 error[E0599]: no method named `as_str` found for type `&&str` in the current scope
   --> $DIR/remove-as_str.rs:17:7
    |
 LL |     s.as_str();
-   |       ^^^^^^ help: try removing `as_str`
+   |       ^^^^^^ try removing `as_str`
 
 error: aborting due to 4 previous errors