Irrelevant column in study ebi_files_sent

[ElDeveloper]

The column ebi_files_sent in the study table is irrelevant and being used in some places in the code-base. Just opening an issue to note that this column is not appropriately updated in the submit_metadata_to_ebi_sra.py script.

@teravest ran a query on the live database and there's only one study that has this flag set to a value different than 0.