Removes an IRCChannel from the internal list when the
bot leaves it.
Remove users from the IRCPluginState.users
array if, by leaving, it left the last channel we can observe it from, so as
not to leak users. It can be argued that this should be part of user awareness,
however this would not be possible if it were not for channel-tracking.
As such keep the behaviour in channel awareness.
Removes an IRCChannel from the internal list when the bot leaves it.
Remove users from the IRCPluginState.users array if, by leaving, it left the last channel we can observe it from, so as not to leak users. It can be argued that this should be part of user awareness, however this would not be possible if it were not for channel-tracking. As such keep the behaviour in channel awareness.