delete old_password_hash in database

[hanabi-live-issues-bot[bot]]

Issue opened by Discord user: Zamiel#8743

[Zamiell]

also set password_hash to NOT NULL

[DrAnax]

1. There are users on the database with NULL on password_hash (last login: 2020-05-08)
2. old_password_hash still exists on the codebase

SELECT users.id, users.username, COUNT(DISTINCT games.id) as num_games FROM games, game_participants, users WHERE games.id = game_participants.game_id AND game_participants.user_id = users.id and users.password_hash IS NULL GROUP BY users.id order by num_games DESC LIMIT 20

[Zamiell]

let's leave it for another year before deleting it