Update docker.io/gabekangas/owncast Docker tag to v0.2.1

No problems automatically updating the Docker image and run the container by Watchtower with dependency update facilitated by Mend's Renovate Bot.

This MR contains the following updates:

Package	Update	Change
docker.io/gabekangas/owncast	patch	`0.2.0` -> `0.2.1`

owncast/owncast (docker.io/gabekangas/owncast)

This is a tiny bugfix release with no features.

Additional v0.2.x releases will continue until the backend refactor work is completed.

Stop the service from running. If you're using a pre-installed image through a hosting provider, or setup Owncast to run under systemd you can probably just simply run systemctl stop owncast.
Change to the directory where Owncast is installed on your server.
If you’ve customized your web interface in any way you will want to back up the files you’ve changed or customized.
Re-run the installer as the user you run Owncast under. For example if you are running owncast as the user "owncast": su -c "curl https://owncast.online/install.sh |bash" owncast
Restart the service. If you're running under systemd systemctl start owncast.

Fix transcoder performance issue that could be experienced. Fixes https://github.com/owncast/owncast/issues/4106
Fix custom theme not applying. Fixes https://github.com/owncast/owncast/issues/4112
Fix admin upgrade message showing when it shouldn't.