use point-in-time instead of retrieved
As discussed at https://www.wikidata.org/wiki/Property_talk:P813 the
retrieved property is not to be used as a qualifier.
Change-Id: Icc005484441aaef50e0233f46c1f6d2d237db0ee
Signed-off-by: Loic Dachary <loic@dachary.org>