Comment describing call_tracer_stocks() is incorrect

[mnlevy1981]

In src/tracer/MOM_tracer_flow_control.F90, the documentation for the subroutine call_tracer_stocks() is identical to that of call_tracer_surface_state() (presumably somebody just copy / pasted the latter to use as a template for the former).

1. Header for call_tracer_surface_state

   !> This subroutine calls all registered tracer packages to enable them to
   !! add to the surface state returned to the coupler. These routines are optional.
   subroutine call_tracer_surface_state(sfc_state, h, G, GV, US, CS)

2. Header for call_tracer_stocks

   !> This subroutine calls all registered tracer packages to enable them to
   !! add to the surface state returned to the coupler. These routines are optional.
   subroutine call_tracer_stocks(h, stock_values, G, GV, US, CS, stock_names, stock_units, &
                                 num_stocks, stock_index, got_min_max, global_min, global_max, &
                                 xgmin, ygmin, zgmin, xgmax, ygmax, zgmax)

This is reflected in the documentation on ReadTheDocs.