Updated VRC Guidelines for Oculus Rift S

We have updated our Rift VRC Guidelines (https://developer.oculus.com/distribute/latest/concepts/publish-rift-app-submission/) to account for Oculus Rift S. Key changes include new frame rate requirements and deprecation of Windows 7 support. For all updates please see the the full update to the Rift VRC Guidelines (https://developer.oculus.com/distribute/latest/concepts/publish-rift-app-submission/) on the Oculus Developer Center.