Remove proxy from repos injection

[szachovy]

For https://ci.suse.de/view/Manager/view/Manager-4.3/job/manager-4.3-qe-sle-update-NUE/ the recent changes in master branch causes pipeline to fail from the following:

[Shell Script -- set +x; source /home/jenkins/.credentials set -x; export TF_VAR_CONTAINER_REPOSITORY=null; export TF_VAR_CUCUMBER_GITREPO=https://github.com/SUSE/spacewalk.git; export TF_VAR_CUCUMBER_BRANCH=Manager-4.3; export TERRAFORM=/usr/bin/terraform; export TERRAFORM_PLUGINS=/usr/bin; ./terracumber-cli --outputdir /home/jenkins/workspace/manager-4.3-qe-sle-update-NUE/results --tf susemanager-ci/terracumber_config/tf_files/SUSEManager-4.3-SLE-update-NUE.tf --gitfolder /home/jenkins/workspace/manager-4.3-qe-sle-update-NUE/results/sumaform --logfile /home/jenkins/workspace/manager-4.3-qe-sle-update-NUE/results/30/sumaform.log --init --taint '.*(domain|main_disk|data_disk|database_disk|standalone_provisioning|server_extra_nfs_mounts).*' --custom-repositories /home/jenkins/workspace/manager-4.3-qe-sle-update-NUE/custom_repositories.json --sumaform-backend libvirt --use-tf-resource-cleaner --tf-resources-to-keep sles15sp4_minion --runstep provision ](https://ci.suse.de/view/Manager/view/Manager-4.3/job/manager-4.3-qe-sle-update-NUE/30/execution/node/32/log)(self time 303ms)
...
09:43:19  + set +x
09:43:19  Running terraform...
09:43:19  ERROR: make sure to have exactly 1 placeholder for additional repositories in susemanager-ci/terracumber_config/tf_files/SUSEManager-4.3-SLE-update-NUE.tf

I used this branch to have a successful pipeline run, feel free to have it adjusted. Merge with the current change will rollback the master.

[srbarrios]

We want to have the ability to inject custom repositories in any kind of node.
I'm not sure when we decided to limit this only to the server, but right now, we must have it on the proxy too, at least for 5.0 due to https://github.com/SUSE/spacewalk/issues/25575#issuecomment-2425937972
https://github.com/SUSE/spacewalk/issues/25575#issuecomment-2429292573

Until we implement:

Deploy a regular minion module with SLE Micro 5.5 instead of using proxy_container module
Onboard that VM as a SLE Micro 5.5 + Proxy 5.0 extension + custom channels (mgr-tools coming from submissions)
We need to fix https://github.com/SUSE/spacewalk/issues/25574
Install mgrpxy package
Missing scenario in the current proxy.feature
Setup proxy container through mgrpxy