remove trailing whitespace

src/fix.cpp

@@ -81,7 +81,7 @@ Fix::Fix(LAMMPS *lmp, int /*narg*/, char **arg) :
   maxexchange_dynamic = 0;
   pre_exchange_migrate = 0;
   stores_ids = 0;
-  
+
   scalar_flag = vector_flag = array_flag = 0;
   peratom_flag = local_flag = 0;
   global_freq = local_freq = peratom_freq = -1;