Merge branch '300031-remove-feature-flag' into 'master'

Remove jira_deployment_issue_keys flag

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127188



Merged-by: Matthias Käppler <mkaeppler@gitlab.com>
Approved-by: Joseph Wambua <jjoshua@gitlab.com>
Approved-by: Ashraf Khamis <akhamis@gitlab.com>
Approved-by: Matthias Käppler <mkaeppler@gitlab.com>
Co-authored-by: Ashraf Khamis <akhamis@gitlab.com>
Co-authored-by: Luke Duncalfe <lduncalfe@gitlab.com>
Co-authored-by: Luke Duncalfe <lduncalfe@eml.cc>