Merge branch '371559-fa-remove-ci_variables_refactoring_to_variable' into 'master'

Remove feature flag ci_variables_refactoring_to_variable

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/97967



Merged-by: Marius Bobin <mbobin@gitlab.com>
Approved-by: Laura Montemayor <lmontemayor@gitlab.com>
Approved-by: Marius Bobin <mbobin@gitlab.com>
Co-authored-by: Furkan Ayhan <furkanayhn@gmail.com>