Remove local copy of xenv as clashing with Python3
LHCb is not planning to make a release on this branch (yet), but we need this change for our legacy nightly builds.
GitLab jobs artifacts no longer stored forever as of Monday, November 4th 08:30h. Further information under https://cern.ch/otg0152576
LHCb is not planning to make a release on this branch (yet), but we need this change for our legacy nightly builds.