Docker: Do not publish master branch Docker images on DockerHub

What

This merge request prevents the publication of Docker image for the master branch in the DockerHub.

The images will still be available in the gitlab registry.

Why

There is no need to have these in the Docker hub. It tends to pollute the repostory.

How

Manually testing the MR

Check #2217910869 master_branch pipeline, especially https://gitlab.com/tezos/tezos/-/jobs/12455826536 and https://gitlab.com/tezos/tezos/-/jobs/12455826544. The images should no appear in https://hub.docker.com/r/tezos/tezos/tags and be pushed as us-central1-docker.pkg.dev/nl-gitlab-runner/registry/tezos/tezos:amd64_killian_docker_remove-master-from-dockerhub.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR