User Story:
As an OpenShift Engineer I want promote vSphere multi disk to GA so we can start officially supporting multiple os disks on vSphere VMs.

Description:
We need to update the API project to have the VSphereMultiDisk feature gate promoted to GA

Acceptance Criteria:
vSphere multi disk is now GA.  This means it should no longer require TechPreview for it to be enabled.

Other Information:
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issue created by splat-bot