Set Selected Repositories For An Organization Variable

Replaces all repositories for an organization variable that is available to selected repositories. Organization variables that are available to selected repositories have their `visibility` field set to `selected`. Authenticated users must have collaborator access to a repository to create, update, or read variables. OAuth app tokens and personal access tokens (classic) need the `admin:org` scope to use this endpoint. If the repository is private, the `repo` scope is also required.