Fix hasFiredAsync parameter when AsyncPlayerSendCommandsEvent is called

[willkroboth]

AsyncPlayerSendCommandsEvent is fired twice, once async, then sync. The javadocs suggest using the logic if (event.isAsynchronous() || !event.hasFiredAsync()) { // do stuff } to only react to the async event.

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However, this check will currently pass during both times the event fires. As seen using this simple plugin:

public final class BukkitTestPlugin extends JavaPlugin implements Listener {
    @Override
    public void onEnable() {
        Bukkit.getServer().getPluginManager().registerEvents(this, this);
    }

    @EventHandler
    public void onCommandsSentToPlayer(AsyncPlayerSendCommandsEvent<?> event) {
        getLogger().info("AsyncPlayerSendCommandsEvent{" +
                "isAsynchronous=" + event.isAsynchronous() +
                ", hasFiredAsync=" + event.hasFiredAsync() + "}"
        );
    }
}

When a player logs in, the event is fired like so:

[07:51:27] [Server thread/INFO]: willkroboth joined the game
[07:51:27] [Server thread/INFO]: willkroboth[/127.0.0.1:41644] logged in with entity id 15 at ([world]-276.5, 72.0, 27.5)
[07:51:27] [Paper Async Command Builder Thread Pool - 0/INFO]: [BukkitTestPlugin] AsyncPlayerSendCommandsEvent{isAsynchronous=true, hasFiredAsync=false}
[07:51:27] [Server thread/INFO]: [BukkitTestPlugin] AsyncPlayerSendCommandsEvent{isAsynchronous=false, hasFiredAsync=false}
[07:52:04] [Server thread/INFO]: Checking version, please wait...
[07:52:05] [Thread-5/INFO]: This server is running Paper version 1.20.6-145-ver/1.20.6@fe7043e (2024-06-15T21:16:04Z) (Implementing API version 1.20.6-R0.1-SNAPSHOT)
You are running the latest version

Both times the event is called, the hasFiredAsync value is false. Therefore !event.hasFiredAsync() is always true, and // do stuff would always run.

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This PR simply makes it so the second time the event is called, hasFiredAsync is true:

[08:27:10] [Server thread/INFO]: willkroboth joined the game
[08:27:10] [Server thread/INFO]: willkroboth[/127.0.0.1:52662] logged in with entity id 126 at ([world]-276.5, 72.0, 27.5)
[08:27:10] [Paper Async Command Builder Thread Pool - 0/INFO]: [BukkitTestPlugin] AsyncPlayerSendCommandsEvent{isAsynchronous=true, hasFiredAsync=false}
[08:27:10] [Server thread/INFO]: [BukkitTestPlugin] AsyncPlayerSendCommandsEvent{isAsynchronous=false, hasFiredAsync=true}
[08:27:19] [Server thread/INFO]: Checking version, please wait...
[08:27:19] [Thread-5/INFO]: This server is running Paper version 1.20.6-DEV-fix-CommandSend-hasFiredAsync@79e2cb6 (2024-06-17T12:19:25Z) (Implementing API version 1.20.6-R0.1-SNAPSHOT)
Unknown version
Previous version: 1.20.6-145-fe7043e (MC: 1.20.6)

With this, if (event.isAsynchronous() || !event.hasFiredAsync()) { // do stuff } will only do stuff during the async event, as the javadocs suggest.

I imagine this is a copy-paste error back from when the event was first added in this commit: fdf41b7#diff-1b1388b7c287d608bf170cd9f7f3ac9477793ac427c444b8968f86e9f4477468R20-R28.

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The javadocs mention If for some reason we are unable to send this asynchronously in the future, only the sync method will fire. If the async call is eventually removed, I imagine the sync event call should have hasFiredAsync set to false (which would then be a correct statement). I believe that is the intended purpose of suggesting the if (event.isAsynchronous() || !event.hasFiredAsync()) { // do stuff } logic, so that // do stuff is still run if the async call is ever removed.