Fixed incorrect property access

refs 0e181c84b2

- the code is already running in the `session` service so it shouldn't access the role property via a non-existing injection

ghost/admin/app/services/session.js

@@ -55,7 +55,7 @@ export default class SessionService extends ESASessionService {
                         resolve({
                             ...event,
                             release: `ghost@${this.config.version}`,
-                            'user.role': this.session.user.role.name
+                            'user.role': this.user.role.name
                         });
                     });
                 });