Synchronously remove project statistic indexes
Summary
In https://gitlab.com/gitlab-com/gitlab-OKRs/-/work_items/7861#note_1926540410 we have identified a number of indexes on project_statistics are not used on GitLab.com:
index_project_statistics_on_repository_size_and_project_idindex_project_statistics_on_storage_size_and_project_idindex_project_statistics_on_packages_size_and_project_idindex_project_statistics_on_wiki_size_and_project_id
The purpose of this issue is to handle the synchronous removal of the indexes once the async removals have completed