Tweak selection algorithm for tests

[Popolechien]

We're running user testing with @dstrinewmf and it would be nice to have a couple of slightly different selection 100 (just for the landing page) to get feedback on:

• A zim with 100 most visited (D-365) x vital_articles;
• A zim with 100 most visited (last 3 years)
• A zim with 100 most visited (3 years) x vital articles

It would be nice to have these 3 in French and English (6 zim files total)

[stale]

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