--admin check for validate-project does not work as expected

[vpchung]

Describe the bug

The project associated with submission ID 9731653 is a publicly accessible Synapse project, but comes back as INVALID when --admin <some user/team> is flagged. e.g.

$ challengeutils validate-project 9731653 syn28590455 --admin "RARE-X Organizers"
INFO:challengeutils.__main__:{'submission_errors': 'Project is private; please update its sharing settings. Writeup should be shared with RARE-X Organizers.', 'submission_status': 'INVALID'}

Expected behavior
Because the project is publicly accessible, the submission should come back as VALID, since the admin team could technically view the project.

Priority
High - needed for the RARE-X challenge which will open soon.