[6.x] Update artisan down output to be consistent with artisan up

[fitztrev]

This makes the output of artisan down like artisan up if there's no change in maintenance mode.

The application was already up, so this is expected behavior:

# Running `up` twice in a row (from a down state)

$ php artisan up
Application is now live.
$ php artisan up
Application is already up.

Effect of this change:

The application was already down:

# Running `down` twice in a row (from an up state)

$ php artisan down
Application is now in maintenance mode.
$ php artisan down
- Application is now in maintenance mode.
+ Application is already down.

It checks the same way the UpCommand.php checks (added via PR #28765)