message: use libCEED restriction for diagonal assembly
  thanks-to: for finding & explaining the issue
diff: @@ -115,7 +115,11 @@ void PABilinearFormExtension::AssembleDiagonal(Vector &y) const
  Array<BilinearFormIntegrator*> &integrators = *a->GetDBFI();
  const int iSz = integrators.Size();
  - if (elem_restrict)
  + bool use_restrict = elem_restrict;
  +#ifdef MFEM_USE_CEED
  + use_restrict = use_restrict && !DeviceCanUseCeed();
  +#endif
  + if (use_restrict)
  {
  localY = 0.0;
  for (int i = 0; i < iSz; ++i)
  