Update gridded seismicity rates

The rates (and possibly b-values) currently in the model are not the annualized rates that we received in an email thread related to conus catalogs. The annualized rates are about 1.5 to two orders of magnitude lower and should significantly reduce differences observed in recent comparisons. The updated rate file is on Teams: Alaska > Catalogs & Gridded Seismicity > Grids > ak-ab-values_annualized.xlsx.

Spreadsheet has been updated with rounding algorithm from ak-ab-values_rounded.xlsx.