fixup! review updates:

examples/multigrid-preconditioned-solver-customized/multigrid-preconditioned-solver-customized.cpp

@@ -136,7 +136,7 @@ int main(int argc, char* argv[])
             .on(exec));
     auto smoother_gen = gko::share(
         gko::solver::build_smoother(ic_gen, 2u, static_cast<ValueType>(0.9)));
-    // Use Pgm as the MultigridLevel factory (this is also the default).
+    // Use Pgm as the MultigridLevel factory.
     auto mg_level_gen =
         gko::share(pgm::build().with_deterministic(true).on(exec));
     // Next we select a CG solver for the coarsest level. Again, since the input