Do not run the pipeline for tags

When you push a package upload, you update the branch and you send an associated tag and the pipeline runs twice for the same commit. This is wasted resources.

We should disable the pipeline for tags. It's just a matter of adding:

except:
  refs:
    - tags

I would have proposed a MR but I will wait until !118 (merged) is merged because it will touch the same part of the code...