Fix watchlist "in the last X hours" display

Fix watchlist "in the last X hours" display

If6280ad6 changed the interpretation of the URL parameter "days=0" (or
any negative value) from meaning "maximum number of days" to actually
meaning "0 days". That's a somewhat annoying breaking change, but easily
worked around by updating bookmarks.

But it didn't update the display on the page, so despite querying 0 days
it would still incorrectly say something like "in the last 720 hours"
rather than "in the last 0 hours".

Bug: T176857
Change-Id: I90c79ef9c4819a34060515b863277fd185828ed9