gmxtopologyreader: remove ancient warning about tpr
gmxtopologyreader: remove ancient warning about tpr

nmols got removed in gromacs/gromacs@8dd3c9ae88004054b3b112c23f747d27a19d8d29

MrTheodor/csg,votca/csg,MrTheodor/csg,votca/csg,votca/csg,votca/csg,MrTheodor/csg,MrTheodor/csg,MrTheodor/csg