[Feature flag] Enable Jira Connect Integration

What

Remove the :jira_connect_app feature flag ...

Owners

• Team: groupproject management in GitLab FOSS
• Most appropriate slack channel to reach out to: #g_plan
• Best individual to reach out to: @engwan

Expectations

What are we expecting to happen?

Enables pushing of commits, branches and MR information to Jira when the app is installed.

What might happen if this goes wrong?

Possible performance issues when pushing commits / creating MRs since the hook here to check for integrations is executed every time

Roll Out Steps

• Enable on staging
• Test on staging
• Ensure that documentation has been updated
• Enable on GitLab.com for individual groups/projects listed above and verify behaviour
• Announce on the issue an estimated time this will be enabled on GitLab.com
• Enable on GitLab.com by running chatops command in #production
• Cross post chatops slack command to #support_gitlab-com and in your team channel
• Announce on the issue that the flag has been enabled
• Remove feature flag and add changelog entry
• After the flag removal is deployed, clean up the feature flag by running chatops command in #production channel