Remove registry migration configuration

What does this MR do?

Remove registry migration configuration

Changelog: removed (cherry picked from commit c489fff6)

We have successfully removed the migration code from the registry in Remove Migration Mode (gitlab-org/container-registry#936 - closed)

We also removed all migration settings from our deployments for .com:

• Remove container registry migration configurati... (gitlab-com/gl-infra/k8s-workloads/gitlab-com!2835 - merged)
• Remove container registry migration configurati... (gitlab-com/gl-infra/k8s-workloads/gitlab-com!2837 - merged)
• Remove container registry migration configurati... (gitlab-com/gl-infra/k8s-workloads/gitlab-com!2844 - merged)

We can now safely remove the migration configuration from the charts 🎉

Related issues

Related to Remove migration configuration from charts (gitlab-org/container-registry#1005 - closed)

Checklist

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.