Remove review-apps related labels from gitlab-org and gitlab-com groups

Context

Part of Epic &19358 - Deprecate/Remove review-apps for gitlab-org/gitlab.

Now that review-apps are being removed, we should clean up related labels that are no longer needed.

Known Labels

• dx::review-apps - Currently in use on multiple issues

Tasks

• Identify all review-apps related labels in gitlab-org group
• Identify all review-apps related labels in gitlab-com group
• Remove dx::review-apps label from existing issues (or leave for historical context?)
• Delete or archive the labels

Questions

• Should we remove the label from existing closed issues, or leave it for historical context?
• Are there any other review-apps related labels beyond dx::review-apps?

Related

• Epic: &19358