Rename `CreateEmptyEmbeddingsRecordsWorker`

This worker creates embeddings records, not empty embeddings records. The name is a result of the original implementation, which created records and then enqueued jobs to fill them.

Now, the worker calls CreateDbEmbeddingsPerDocFileWorker once for each docs file, which in turn creates the DB records. So the word Empty in the name is confusing.

This worker is only called once a day via cron but we should still be careful when renaming it. The safest path is probably to add the new, renamed worker as a duplicate of the old and call it via cron. Then remove the old worker in the next release. See docs on removing workers.