[FEAT] Rename repository to reflect upstream project name

[rig0a]

Is this a new feature request?

• I have searched the existing issues

Wanted change

Rename the repository to reflect the upstream project - https://github.com/owntone/owntone-server

Reason for change

The upstream project was renamed at release 28.0, dated 22/05/2021

This repository was modified to reflect that upstream change in PR #51, but this image and repo retain the old name docker-daapd; I would be in favour of updating the name as the software offers more than just a DAAP server

Proposed code change

I do not know what precedent exists for linuxserver.io to rename existing containers

I assume the reason it hasn't been done is it creates a breaking change for end users

Would this only be acheivable by deprecating docker-daapd and creating a new docker-owntone as a replacement?

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[aptalca]

This image has been on the verge of deprecation for a long time now. No one on the team uses it, including the current maintainer. That's why we never published it under its new name.

[ejurgensen]

There is an official image now, so sounds like a good idea to deprecate this