Clean up snicar-ad shortwave settings

[eclare108213]

1. Icepack fully hard-coded the input data needed for the 5-band snicar-ad shortwave radiation calculation when Icepack was merged with the old MPAS-seaice column physics. E3SM uses that hard-coded data but was not modified to stop reading the old data files. To use the read-in data, the files would need to be updated to include all of the associated data that was hard-coded in E3SM prior to the merge, and Icepack would need to be modified to receive the data through its interface with the driver (MPAS-seaice). Until those modifications are made (if they are made), it would be better to clean up the code.

2. Remove the cpp USE_SNICARHC set in E3SM, which is the default condition in Icepack. (Note: this will need to be done when Icepack is resynced -- using it is correct at the moment in E3SM)

See more detailed comments regarding this issue in #6668