[RB_files] Inconsistency between SQL and RB_physiological_output_type

[jeffersoncasimir]

According to the BIDS spec, and consistent with the SQL, derivative should be spelled without an s.

The fix on the aces/Loris side is to change derivatives to derivative in RB_physiological_output_type.

Related Loris-MRI issue: https://github.com/aces/Loris-MRI/issues/1118