Do not autobump version now that unified CI manages releases

[masih]

The unified CI, now integrated in this repo, manages releases and version bumps via version.json file. At the same time there is a CI job that tags every push to main.

We should disable that auto tagging and converge on using the unified CI mechanism unless there is a good reason for it.

singularity/.github/workflows/autobump.yml

Line 15 in 563fbc1

- name: Bump version and push tag

[xinaxu]

Makes sense. Removed in #122

[xinaxu]

pending doc update to use ghcr.io instead of dockerhub