reset manybody_flag if threebody terms are turned on or off in sw pair style

src/MANYBODY/pair_sw.cpp

@@ -250,6 +250,7 @@ void PairSW::settings(int narg, char ** arg)
       // pair_coeff * * and can enable the single function.
       one_coeff = skip_threebody_flag ? 0 : 1;
       single_enable = skip_threebody_flag ? 1 : 0;
+      manybody_flag = skip_threebody_flag ? 0 : 1;
       iarg += 2;
     } else error->all(FLERR, "Illegal pair_style sw keyword: {}", arg[iarg]);
   }