Spec test failures with duplicate migrations

Summary

Example failed test: https://gitlab.com/charts/gitlab/-/jobs/146900396

This is very likely due to our tests running migrations after backup https://gitlab.com/charts/gitlab/blob/master/spec/features/backups_spec.rb#L10

While the operator is still running the post-migrations.

Ideally we should come up with a way for the tests to wait for the migrations from the deployment to be fully complete before they start their test run.