[Feature flag] Enable the flag that hides the jump to next unresolved discussion on the thread/comment box

What

Remove the :hide_jump_to_next_unresolved_in_threads feature flag ...

Owners

• Team: Create: Source Code
• Most appropriate slack channel to reach out to: #g_create_source-code
• Best individual to reach out to: @sming-gitlab

Expectations

### What are we expecting to happen?

Jump to next unresolved discussion disappears from the comment box (next to Resolve button).

What might happen if this goes wrong?

Some features around this functionality acting differently than expected.

What can we monitor to detect problems with this?

Issues reporting problems with Jump to Next Discussion.

Beta groups/projects

If applicable, any groups/projects that are happy to have this feature turned on early. Some organizations may wish to test big changes they are interested in with a small subset of users ahead of time for example.

• gitlab-org/gitlab project
• gitlab-org/gitlab-com groups
• ...

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
• Coordinate a time to enable the flag with #production and #g_delivery on slack.
• 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 (more guidance when this is necessary in the dev docs) 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