remove inactive characters from leaderboard

[Muparadzi]

once a character has achieved a certain rating, they can go inactive and essentially reserve a place on the leaderboard.

glicko2 provides a mechanism to better calculate inactivity through a value called rating deviation or RD. this value should be increasing when players are inactive, currently it will only increase when a player is in a game but does not have any rating adjustment.

perhaps we should just remove inactive players from the leaderboard query response