Sets PETSc to not display warnings for unused options

Starting from PETSc 3.20 this warning is triggered by non-PETSc
command line options, which is not desired.

src/utils/PETScWrapper.cpp

@@ -16,6 +16,7 @@ initialize([[maybe_unused]] int& argc, [[maybe_unused]] char* argv[])
   PETSC_COMM_WORLD = parallel::Messenger::getInstance().comm();
   PetscOptionsSetValue(NULL, "-no_signal_handler", "true");
   PetscOptionsSetValue(NULL, "-fp_trap", "false");
+  PetscOptionsSetValue(NULL, "-options_left", "false");
   PetscInitialize(&argc, &argv, 0, 0);
 #endif   // PUGS_HAS_PETSC
 }