[Feature flag] Rollout update nodes optimization feature for banzai reference filter

What

Remove the :update_nodes_for_banzai_reference_filter feature flag ...

Owners

• Team: Memory Team
• Most appropriate slack channel to reach out to: #g_memory
• Best individual to reach out to: @nmilojevic1

Expectations

### What are we expecting to happen? BlobController#Show action should work as before, with improved performance. Also, this will affect all other places where we use markup, like File Preview, Issue Preview, creating notes...

What might happen if this goes wrong?

In case something goes wrong, rendered HTML markup could be broken. In the case of descriptions and comments, we store the result of this filtered rendered markdown in the DB. So if something is wrong here, we'd have to invalidate the DB cache too.

Links

• https://log.gprd.gitlab.net/goto/b9960d231bcfd86b0570cb29471749ba

Beta groups/projects

I will enable this feature on:

• gitlab-com/www-gitlab-com project
• gitlab-org/gitlab project
• gitlab-org/gitlab-foss 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 the 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

Related to: ##217580 (closed)