clean up "GEOSldas.GRID_TYPE=LatLon" in LDAS.rc when used with EASE grids

[gmao-rreichle]

MAPL does not yet provide full functionality for EASE grids.
For now, GEOSldas uses some but not all of MAPL's LatLon functionality to handle EASE grids.
Once EASE grids can be handled by MAPL, clean up the "GRID_TYPE" in LDAS.rc.

[gmao-rreichle]

still waiting for MAPL capability to handle EASE grids...

[biljanaorescanin]

This was addressed by this PR @weiyuan-jiang did: GEOS-ESM/MAPL#3698
See also GEOS-ESM/GEOSldas_GridComp#115