use the new version of 'archivebot-older-than'

with the 'duration' parameter

per mailing list:
http://comments.gmane.org/gmane.comp.python.pywikipediabot.general/14160

corresponding change in the i18n file:
I507b0b38a87fe8e97b850a71d9c1764ec16fbeb1

backport of Ie4699550def701a728abaca3e62287e1c36ce3b0 from core

Change-Id: Ifefc1c289120edd62747480cee497f846e6810c8