Enable code_navigation_references feature flag by default

What

Enable the :code_navigation_references feature flag introduced in #217392 (closed) by default.

Owners

• Team: groupsource code
• Most appropriate slack channel to reach out to: #g_create_source-code
• Best individual to reach out to: @patrickbajao

Expectations

### What are we expecting to happen?

LSIF json files will still be generated for those projects with code intelligence enabled.

What might happen if this goes wrong?

No LSIF json files will be generated.

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-shell project
• gitlab-org/gitlab-workhorse project

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 (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
• Enable feature flag by default