Fix app-rejected and app-submitted

[andrlime]

The app-submitted and app-rejected folders seem not applicable to this competition. Figure out what to do with them and implement a fix, such that these pages either don't exist, or the content is updated to be applicable to FinRL.

[echavemann]

I think we should still have acceptances right? @stellawang196 to confirm but I think we would want to validate that they are attendees?

[stellawang196]

If your "app" means team registration application to participate in the contest, I think after submitting registration application, they will be checked to see if each member has already registered in a team before. If not, the registration application will be accepted. But we may not select participants.