note why we dont try to compile this test

Author: coke

doc/Language/typesystem.pod6

@@ -226,7 +226,7 @@ X«|only method»
 
 To explicitly state that a method is not a multi method use the C<only method> declarator.
 
-=for code :skip-test
+=for code :skip-test<compile time error>
 class C {
     only method m {};
     multi method m {};