RuboCop: Update TargetRubyVersion to Ruby 3.2

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/172715



Merged-by: Gavin Hinfey <ghinfey@gitlab.com>
Approved-by: Tiger Watson <twatson@gitlab.com>
Approved-by: David Dieulivol <ddieulivol@gitlab.com>
Approved-by: Gavin Hinfey <ghinfey@gitlab.com>
Co-authored-by: Peter Leitzen <pleitzen@gitlab.com>