Clean up E0454

Author: GuillaumeGomez

src/librustc_error_codes/error_codes/E0454.md

@@ -1,4 +1,6 @@
-A link name was given with an empty name. Erroneous code example:
+A link name was given with an empty name.
+
+Erroneous code example:
 
 ```compile_fail,E0454
 #[link(name = "")] extern {}