Remove hierarchy_stoplist in favour of always_direct

Remove hierarchy_stoplist in favour of always_direct

This directive was deprecated 2 years (and versions) ago. It can be
replaced with:
  acl stoplist url_regex cgi-bin|\?
  always_direct allow stoplist

The major difference between the two configurations is that the old
hierarchy_stoplist was applied after never_direct and always_direct is
applied before it. Both override the never_direct result, so this is not
a problem.