Remove feature flag and add changelog

And update translations

changelogs/unreleased/273726-feature-flag-remove-jira_issues_list.yml

+---
+title: Update Jira issues list to use new UI components
+merge_request: 56465
+author:
+type: changed

config/feature_flags/development/jira_issues_list.yml

----
-name: jira_issues_list
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/45678
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/273726
-milestone: '13.6'
-type: development
-group: group::ecosystem
-default_enabled: false

locale/gitlab.pot

@@ -8815,9 +8815,6 @@ msgstr ""
 msgid "Create new file or directory"
 msgstr ""
 
-msgid "Create new issue in Jira"
-msgstr ""
-
 msgid "Create new label"
 msgstr ""