Remove metrics and usage_data config for Static Site Editor

Follow up from !87221 (comment 952157951)

• MR to remove metrics and usage data: Remove metrics for SSE feature (!88485 - merged)
• MR to check for dashboard usage: https://gitlab.com/gitlab-data/analytics/-/issues/12899+

See also: https://docs.gitlab.com/ee/development/service_ping/metrics_lifecycle.html#remove-a-metric