Clean up E0367 explanation

Author: GuillaumeGomez

src/librustc_error_codes/error_codes/E0367.md

@@ -1,8 +1,9 @@
 An attempt was made to implement `Drop` on a specialization of a generic type.
-An example is shown below:
+
+Erroneous code example:
 
 ```compile_fail,E0367
-trait Foo{}
+trait Foo {}
 
 struct MyStruct<T> {
     t: T