Lock the bundler version as omnibus
In CE master: https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/50502378
We're using:
Using bundler 1.16.1
However the version is different on omnibus: (1.13.7
at the moment)
https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/config/software/bundler.rb
This is discovered from omnibus-gitlab#3128 (comment 57070851)