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

Change-Id: Ie4699550def701a728abaca3e62287e1c36ce3b0
Merge "use the new version of 'archivebot-older-than'"