Find all references to the `container.tar.gz` file, and replace them
with references to `container.tar`. Moreover, remove the `--no-save`
argument of `build-image.py` since we now always save the image.
Finally, fix some stale references to Poetry, which are not necessary
anymore.
This directory holds some scripts that are helpful for developing on Dangerzone.
Read the respective documentation for more details on some of the scripts.