Fix variable name in iceberg climatologies

[xylar]

bergFreshWaterFluxData --> bergFreshwaterFluxData

Checklist

• Document (in a comment titled Testing in this PR) any testing that was used to verify the changes

[xylar]

Testing

I ran through files_for_e3sm using the QU240 mesh and see:

$  pwd
/lcrc/group/e3sm/ac.xylar/compass_1.2/chrysalis/test_20231018/qu240-fix-iceberg/ocean/global_ocean/QU240/WOA23/files_for_e3sm/assembled_files/inputdata/ice/mpas-seaice/QU240E3r1
$ ncdump -h Iceberg_Climatology_Merino.QU240E3r1.20231018.nc | more
netcdf Iceberg_Climatology_Merino.QU240E3r1.20231018 {
dimensions:
	Time = UNLIMITED ; // (12 currently)
	nCells = 7404 ;
	StrLen = 64 ;
variables:
	double lat(nCells) ;
		lat:long_name = "Latitude of Grid Cell Centers" ;
		lat:standard_name = "latitude" ;
		lat:units = "degrees_north" ;
		lat:axis = "Y" ;
		lat:valid_min = -90. ;
		lat:valid_max = 90. ;
		lat:bounds = "lat_vertices" ;
	double lon(nCells) ;
		lon:long_name = "Longitude of Grid Cell Centers" ;
		lon:standard_name = "longitude" ;
		lon:units = "degrees_east" ;
		lon:axis = "X" ;
		lon:valid_min = 0. ;
		lon:valid_max = 360. ;
		lon:bounds = "lon_vertices" ;
	double area(nCells) ;
		area:long_name = "Solid angle subtended by gridcell" ;
		area:standard_name = "solid_angle" ;
		area:units = "steradian" ;
		area:cell_mathods = "lat, lon: sum" ;
		area:coordinates = "lat lon" ;
	float bergFreshwaterFluxData(Time, nCells) ;
		bergFreshwaterFluxData:units = "Kg/m2/s" ;
		bergFreshwaterFluxData:cell_measures = "area: area" ;
		bergFreshwaterFluxData:coordinates = "lat lon" ;
	char xtime(Time, StrLen) ;
...