Allow admins to call set org user role mutation

[BartoszJarocki]

This change will allow admin users to set org billing users using the following mutation

mutation {
   setOrgUserRole(orgId: "orgId", userId: "local|botpRdWlzi", role: "BILLING_LEADER") {
      updatedOrgMember {
         user {
           email
         }
       }
   }
}

context: https://parabol.slack.com/archives/C4JAUUZ9P/p1646147430342679

[BartoszJarocki]

@mattkrick would you mind taking a look? 🙏

[mattkrick]

LGTM!