zope4: HelpSys has been removed from Zope.

For now, remove it completely. If necessary `registerHelp()` can be used.

  commit f3ab4409bfa9a3e1943099c8ae391a2f0273b53b
  Date:   Sat Jul 2 18:26:53 2011 +0000
    Removed the old help system, in favor of the current Sphinx documentation
    hosted at http://docs.zope.org/zope2/. For backwards compatibility the
    `registerHelp` and `registerHelpTitle` methods are still available on the
    ProductContext used during the `initialize` function.