Contract 6.21.1

Two note wordings from 6.21.0, and the duel repair done.

• battles_query's vs note says again that starting_trophies is what matchmaking paired on ladder, and the unequal-towers note says the tower levels differ.
• The recorded duels are recomputed on games won: 140 duels, 280 player-days of daily totals.

Wording and data; no shape change.