Remove redundant units='none' arguments in register_*_field calls

[uramirez8707]

In some register_*_field calls in full,simple/atm_land_ice_flux_exchange.F90, the optional argument units is pass in as "none":

FMScoupler/full/atm_land_ice_flux_exchange.F90

Lines 3382 to 3409 in 7c47be3

	id_land_mask = &
	register_static_field ( mod_name, 'land_mask', atmos_axes, &
	'fractional amount of land', 'none', &
	range=frange, interp_method = "conserve_order1" )
	!--------- initialize diagnostic fields --------------------
	id_ice_mask = &
	register_diag_field ( mod_name, 'ice_mask', atmos_axes, Time, &
	'fractional amount of sea ice', 'none', &
	range=frange, interp_method = "conserve_order1" )
	id_wind = &
	register_diag_field ( mod_name, 'wind', atmos_axes, Time, &
	'wind speed for flux calculations', 'm/s', &
	range=(/0.,vrange(2)/) )
	id_drag_moist = &
	register_diag_field ( mod_name, 'drag_moist', atmos_axes, Time, &
	'drag coeff for moisture', 'none' )
	id_drag_heat = &
	register_diag_field ( mod_name, 'drag_heat', atmos_axes, Time, &
	'drag coeff for heat', 'none' )
	id_drag_mom = &
	register_diag_field ( mod_name, 'drag_mom', atmos_axes, Time, &
	'drag coeff for momentum', 'none' )

This is redundant because, diag manager does not write it anyway:
https://github.com/NOAA-GFDL/FMS/blob/203c8bf464ff26fe0fe39b1451caedd026bbce55/diag_manager/diag_output.F90#L651-L652

Dimensionless variables are not required to have units to be cf compliant. I think these units='none' arguments should be removed from the register_*field calls. It won't change any behavior.