db

`index_lfs_objects_projects_on_project_id_lfs_object_id_null_repo_type`
was already created asynchronously in [a prior post-deployment migration](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/177919)

This commit ensures that it is properly created synchronously
for all installations, updating the schema definition accordingly.
[Reference](https://docs.gitlab.com/development/database/adding_database_indexes/#schedule-index-creation-for-a-low-impact-time)