[CI] Fix AATH excessive image creation

[gmulhearn]

Currently on every commit to master the CI will create a new image and tag it with main. However, on retagging, it will leave a dangling image for previous commits that are now tagless. https://github.com/hyperledger/aries-vcx/pkgs/container/aries-vcx%2Faath-backchannel/versions

Ideally we clean up those dangling images, we don't really need a full history of images for each commit at this point