Revert "add scc-air-gapped option"

This reverts merge request !431 (merged)

The reason is that the change in pre/post Commands results in a delta between what is generated from bootstrap context and from mgmt context, resulting in an unwanted node rolling update after pivot.

Reported by @vladimir.braquet on Slack #dev channel today;

In the mgnt cluster case:

  pre_bootstrap_commands:
    - |
      echo ">> Installing miniserve for log collection in CI"
      (
      export https_proxy=http://172.20.136.219:3128
      export no_proxy=100.72.0.0/16,100.73.0.0/16,repos.tech.orange,docker,.cluster.local,.cluster.local.,.svc,.sylva,10.0.0.0/8,127.0.0.1,172.16.0.0/12,192.168.0.0/16,localhostIn the bootstrap case:

additional_commands:
  pre_bootstrap_commands:
    - |
      echo ">> Installing miniserve for log collection in CI"
      (
      export https_proxy=http://172.20.136.219:3128
      export no_proxy=100.72.0.0/16,100.73.0.0/16,repos.tech.orange,docker,.cluster.local,.cluster.local.,.svc,.sylva,10.0.0.0/8,100.100.0.0/16,100.96.0.0/16,127.0.0.1,172.16.0.0/12,192.168.0.0/16,localhost

Closes sylva-projects/sylva-core#4179 (closed)