[406-rmv-overlap-line-for-dg2] rmv single procsets

src/lib2_mesh/distribution/Overlap.cpp

@@ -752,4 +752,5 @@ void Overlap::CellsOverlap_dG2(Mesh &mesh) const {
       delete C;
     }
   }
+  mesh.procSets.RemoveSingle();
 }