Remove fms_io_mod entries from ice_ridge.F90

ice_ridge contained unused references to fms_io_mod, which is to be
removed from FMS.  This patch removes those lines.

src/ice_ridge.F90

@@ -24,7 +24,6 @@ module ice_ridging_mod
 use MOM_unit_scaling,  only : unit_scale_type
 use SIS_hor_grid,      only : SIS_hor_grid_type
 use SIS_types,         only : ice_state_type, ist_chksum
-use fms_io_mod,        only : register_restart_field, restart_file_type
 use SIS_tracer_registry, only : SIS_tracer_registry_type, SIS_tracer_type, get_SIS_tracer_pointer
 use SIS2_ice_thm,      only : get_SIS2_thermo_coefs
 use ice_grid,          only : ice_grid_type