Listen to token changes instead of conversation object
Listen to token changes instead of conversation object

The converstion watcher is triggered even for attribute changes, so we
now use the token watcher instead for scrolling up so it only happens
when meaningful.

Signed-off-by: Vincent Petry <87e1f221a672a14a323e57bb65eaea19d3ed3804@nextcloud.com>

nextcloud/spreed,nextcloud/spreed,nextcloud/spreed