Mark code as skip-test

- Since unlink touches the filesystem

Author: zoffixznet

doc/Language/traps.pod6

@@ -738,7 +738,7 @@ and then stringify an L<IO::Path>, or stringify an L<IO::Path> with custom
 C<$!CWD> attribute, the resultant string won't reference the original
 filesystem object:
 
-=begin code
+=begin code :skip-test
     with 'foo'.IO {
         .Str.say;       # OUTPUT: «foo␤»
         .relative.say;  # OUTPUT: «foo␤»