Removed buildout.dumppickedversions from the warning. Partial fix for #70

I *have* retained buildout.dumppickedversions in the doctest with
the qualification 'only part of it'.

Removing the warning *does* make it less obvious for the people
that use buildout.dumppickedversions in the way I thought it
was used most, but apparently the default behaviour of dumppickedversions
was otherwise.