force setting petsc pre per cmd option

src/hyteg/petsc/PETScCGSolver.hpp

@@ -115,8 +115,6 @@ class PETScCGSolver : public Solver< OperatorType >
          MatSetNullSpace( Amat.get(), nullspace_ );
       }
       KSPSetOperators( ksp, Amat.get(), Amat.get() );
-      KSPGetPC( ksp, &pc );
-      PCSetType( pc, PCJACOBI );
 
       x.getStorage()->getTimingTree()->start( "PETSc CG Solver Apply" );
       KSPSolve( ksp, bVec.get(), xVec.get() );