cleanup(pkgrepo) remove last remnants of blobxfer

[dduportal]

Related to jenkins-infra/helpdesk#3414

This PR removes the last remnants of blobxfer from the Puppet management.
Once deployed, it will allow jenkins-infra/mirror-scripts#25 to be merged and deployed.

Note: the following cleanup procedure is needed once the PR is merged as Puppet is not setup to "remove" files/packages (the PR only removes the management). This procedure has been tested on the local Vagrant VM but of course it might differ from reality.

• Packages to remove (It should NOT remove letsencrypt as the python3.8 Python installation is shared): virtualenv, python3.8-venv, python3.8-dev, libffi-dev:

apt remove --purge virtualenv python3.8-venv python3.8-dev libffi-dev
apt autoremove --purge

• Files/dir: /srv/releases/.venv-blobxfer, /srv/releases/requirements.txt (symlink to mirror-scripts), /srv/releases/batch-upload.bash (symlink):

rm -rf /srv/releases/.venv-blobxfer
unlink /srv/releases/batch-upload.bash
unlink /srv/releases/requirements.txt

• cleanup: remove last remnants of blobxfer mirror-scripts#25