Allow platform admins to disable repos

[KellyMerrick]

Description

Platform admins can disable repos via the database, but not via Vela.

The ability to disable will likely not mirror a repo admin's ability to disable, as a platform admin may not have the same scm permissions as the repo admin (therefore, may not be able to delete the webhook).

At a minimum, allow a platform admin to disable the repo in the database via Vela.

Value

Platform admins do not need to directly hit the database to disable a repo.

Definition of Done

Platform admins can disable a repo via ui/api/cli.

Effort (Optional)

Impacted Personas (Optional)