remove finished_at migrations
As per the comment https://github.com/huggingface/datasets-server/pull/2175#discussion_r1412342252, remove finishet_at migrations will be handled in a separate PR.
Depends on https://github.com/huggingface/datasets-server/pull/2178

remove finished_at migrations: As per the comment https://github.com/huggingface/datasets-server/pull/2175#discussion_r1412342252, remove finishet_at migrations will be handled in a separate PR.
Depends on https://github.com/huggingface/datasets-server/pull/2178
