Remove patch of _delObj on PluggableAuthSerive

[jensens]

In code pas.py there was already a comment, no more to say:

# for ZopeVersionControl, we need to check 'plugins' for more than
# existence, since it replaces objects (like 'plugins') with SimpleItems
# and calls _delOb, which tries to use special methods of 'plugins'
def _delOb(self, id):
    #
    #   Override ObjectManager's version to clean up any plugin
    #   registrations for the deleted object
    #
    # XXX imo this is a evil one
    #

[gforcada]

And actually you were the one adding that "XXX imo this is a evil one": d4ed704

[jensens]

yeah indeed, but the above information is more interesting