update sexual dimorphism studies' EFO

[earlEBI]

The following studies are annotated with a 'quality' EFO (EFO_0005951). A new measurement EFO (EFO_0021796) has been created which should replace this quality term. The quality term can be removed from db.

GCST005363 GCST002063

Note: both studies have background EFOs which should remain as they are.

(I can't update these myself because they are so old they don't have submissions attached, and the newly added EFOs don't appear in the curation app EFO dropdown.)