Polish

`read_field_indices` is now called from `shpc_open` so the comment
no longer makes sense.

Common/read_snapshot.f90

@@ -7,8 +7,6 @@ contains
   subroutine read_snapshot(s, hshp, nlon, nlat, d_init, k, corner, step, copy, &
        ishape_last)
 
-    ! Note: read_field_indices must have been called before read_snapshot.
-
     ! Libraries:
     use contour_531, only: convert_to_ind 
     use nr_util, only: assert