communities api: remove owned_by

[tmorrell]

❤️ Thank you for your contribution!

Description

owned_by was removed in 2022 in inveniosoftware/invenio-communities@14c4768#diff-fdb214e572f1f6740d9290cb190a449bf6abd4da7073797e349df6836a31052e.

This will need to be backported to production.

Checklist

Ticks in all boxes and 🟢 on all GitHub actions status checks are required to merge:

• I'm aware of the code of conduct.
• I've created logical separate commits and followed the commit message format.
• I've targeted the master branch.
• If this documentation change impacts the current release of InvenioRDM, I will backport it to the production branch following approval or indicate to a maintainer that it should be backported.

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[fenekku]

Right, thanks for that!