rustdoc: remove excess from rustdoc test

Author: megakorre

tests/rustdoc-ui/mismatched_arg_count.rs

@@ -1,5 +1,3 @@
-// ensures that we don't ICE when there are too many args supplied to the alias.
-
 trait Trait<'a> {
     type Assoc;
 }
@@ -8,5 +6,3 @@ type Alias<'a, T> = <T as Trait<'a>>::Assoc;
 
 fn bar<'a, T: Trait<'a>>(_: Alias<'a, 'a, T>) {}
 //~^ error: type alias takes 1 lifetime argument but 2 lifetime arguments were supplied
-
-fn main() {}

tests/rustdoc-ui/mismatched_arg_count.stderr

@@ -1,13 +1,13 @@
 error[E0107]: type alias takes 1 lifetime argument but 2 lifetime arguments were supplied
-  --> $DIR/mismatched_arg_count.rs:9:29
+  --> $DIR/mismatched_arg_count.rs:7:29
    |
 LL | fn bar<'a, T: Trait<'a>>(_: Alias<'a, 'a, T>) {}
    |                             ^^^^^     -- help: remove this lifetime argument
    |                             |
    |                             expected 1 lifetime argument
    |
 note: type alias defined here, with 1 lifetime parameter: `'a`
-  --> $DIR/mismatched_arg_count.rs:7:6
+  --> $DIR/mismatched_arg_count.rs:5:6
    |
 LL | type Alias<'a, T> = <T as Trait<'a>>::Assoc;
    |      ^^^^^ --