Cleanup av_player on profile close

[kelciour]

To reproduce the issue, a profile needs to be opened and closed several times.

The list of players will keep growing in size and include the list of players that were previously instantiated but were shut down on profile close a bit later.

from aqt.sound import av_player

for i, p in enumerate(av_player.players, 1):
  print(i, p)

Before

After

[YukiNagat0]

self.players.clear() will be more "pythonic" way to do it.

[kelciour]

Thank you! It's been changed.