[Feature flag] Clean up devops_adoption_feature

Problem to solve

The devops_adoption_feature feature flag is for instance-level DevOps Adoption. This feature flag was enabled by default under #325795 (closed), but it has not yet been cleaned up (removed).

Proposal

Clean up (remove) all references to the devops_adoption_feature feature flag.

• Create a merge request to remove devops_adoption_feature feature flag. Ask for review and merge it.
  • Remove all references to the feature flag from the codebase.
  • Remove the YAML definitions for the feature from the repository.
  • Create a changelog entry.
  • Update the DevOps Adoption docs according to the feature flag documentation guidelines.
• Ensure that the cleanup MR has been deployed to both production and canary. If the merge request was deployed before the code cutoff, the feature can be officially announced in a release blog post.
  • /chatops run auto_deploy status <merge-commit-of-cleanup-mr>
• Close the feature issue to indicate the feature will be released in the current milestone.
• Clean up the feature flag from all environments by running these chatops command in #production channel:
  • /chatops run feature delete devops_adoption_feature --dev
  • /chatops run feature delete devops_adoption_feature --staging
  • /chatops run feature delete devops_adoption_feature
• Close this rollout issue.