Fixed stylistic convention for one diagnostic and blessed tests.

Author: Alexander Regueiro

src/librustc_typeck/astconv.rs

@@ -952,8 +952,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         tcx.sess.span_warn(
                             span,
                             "default bound relaxed for a type parameter, but \
-                            this does nothing because the given bound is not \
-                            a default. Only `?Sized` is supported",
+                             this does nothing because the given bound is not \
+                             a default; only `?Sized` is supported",
                         );
                     }
                 }

src/test/ui/issues/issue-37534.stderr

@@ -8,7 +8,7 @@ help: possible better candidate is found in another module, you can import it in
 LL | use std::hash::Hash;
    |
 
-warning: default bound relaxed for a type parameter, but this does nothing because the given bound is not a default. Only `?Sized` is supported
+warning: default bound relaxed for a type parameter, but this does nothing because the given bound is not a default; only `?Sized` is supported
   --> $DIR/issue-37534.rs:1:12
    |
 LL | struct Foo<T: ?Hash> { }

src/test/ui/maybe-bounds-where.stderr

@@ -34,7 +34,7 @@ error[E0203]: type parameter has more than one relaxed default bound, only one i
 LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
    |           ^
 
-warning: default bound relaxed for a type parameter, but this does nothing because the given bound is not a default. Only `?Sized` is supported
+warning: default bound relaxed for a type parameter, but this does nothing because the given bound is not a default; only `?Sized` is supported
   --> $DIR/maybe-bounds-where.rs:15:11
    |
 LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;