The GroupContent Delete API has been deprecated in favour of Create with the status 'Removed'.
However, it is not possible to fully 'Delete' a contact from a group using the API. The GroupContact BAO looks for the 'Deleted' status passed to the function, rather than 'Removed'. But using 'Deleted' results in the API error:
"Deleted' is not a valid option for field status"
This is because 'Deleted' isn't a real value (as noted in the deprecated Delete API function).