No more updates to master branch in github.com/opencast/opencast-docker

[mtneug]

As announced in #6478, the branching structure in https://github.com/opencast/opencast-docker changed. With the release of Opencast 18.0, I will therefore no longer update the master branch. Please use main, the version branches {version}.x or release branches {version}.{minor_version} instead.

I will delete the master branch with the release of Opencast 19.0.

– Matthias