chore(shorebird_cli): update 'app not found' message to better reflect collaborator support (#724)

packages/shorebird_cli/lib/src/code_push_client_wrapper.dart

@@ -63,12 +63,10 @@ class CodePushClientWrapper {
   Future<AppMetadata> getApp({required String appId}) async {
     final app = await maybeGetApp(appId: appId);
     if (app == null) {
-      // TODO(bryanoltman): improve this error message to indicate that a user
-      // may not have permission to view the app.
       logger.err(
         '''
 Could not find app with id: "$appId".
-Did you forget to run "shorebird init"?''',
+This app may not exist or you may not have permission to view it.''',
       );
       exit(ExitCode.software.code);
     }