message: Fix typo in error message in 'platform status'.
diff: @@ -302,7 +302,7 @@ protected:
  platform_sp->GetStatus(ostrm);
  result.SetStatus(eReturnStatusSuccessFinishResult);
  } else {
  - result.AppendError("no platform us currently selected\n");
  + result.AppendError("no platform is currently selected\n");
  result.SetStatus(eReturnStatusFailed);
  }
  return result.Succeeded();
  