v12: Remove Old Dynamical Cores

[mathomp4]

It is time to remove ARIES and the FV latlon cores from GEOSgcm. This issue will track the needed changes.

So far:

• GEOSgcm: v12: Remove ARIES and Latlon cores #1014
• GEOSgcm_GridComp: v12: Remove ARIES and LatLon dynamics GCs GEOSgcm_GridComp#1174
• GEOSgcm_App: v12: Remove reference to FV latlon core GEOSgcm_App#789

We also need to remove the sparse lines for these directories in the fixture.

[mathomp4]

I will mention @sdrabenh so he knows and @wmputman in case he has objections.