If the number of repositories is high, Gitlab pagination may limit to 20
repositories per page. In that case, ci-fairy was getting a partial list
and deleted images only for those repositories. Even specifying
--repository it had the same effect.

Pass `get_all=True` to repositories.list() so the full list of
repositories is retrieved.

Without the fix, a warning message is printed if you are getting a
partial list:
    UserWarning: Calling a `list()` method without specifying `get_all=True`
    or `iterator=True` will return a maximum of 20 items. Your query returned
    20 of 42 items. See https://python-gitlab.readthedocs.io/en/v3.14.0/api-usage.html#pagination
    for more details. If this was done intentionally, then this warning can
    be supressed by adding the argument `get_all=False` to the `list()` call.
    (python-gitlab: /usr/lib/python3.12/site-packages/gitlab/client.py:976)
      r for r in p.repositories.list() if repository is None or repository == r.name