Merge branch 'sh-use-bundler' into 'master'

Use bundler to install Omnibus gems

See merge request https://gitlab.com/gitlab-org/omnibus-gitlab/-/merge_requests/7362

Merged-by: Balasankar 'Balu' C <balasankar@gitlab.com>
Approved-by: Balasankar 'Balu' C <balasankar@gitlab.com>
Reviewed-by: Balasankar 'Balu' C <balasankar@gitlab.com>
Reviewed-by: Robert Marshall <rmarshall@gitlab.com>
Co-authored-by: Stan Hu <stanhu@gmail.com>

Author: balasankarc