Update MOM6 after https://github.com/mom-ocean/MOM6/pull/1556 is merged

[sanAkel]

This is currently a note to myself (@sanAkel).

It should be undrafted after: @marshallward and co. have finished merging mom-ocean/MOM6#1556 into dev/gfdl

In order for GEOS-ESM to use ⬆️ following sequence of steps need to happen in this order:

1. @sanAkel make a new release of GEOS-MOM6 ✅ https://github.com/GEOS-ESM/MOM6/releases/tag/geos%2Fv2.0.3
2. Simultaneously undraft this PR ➡️ this will update our cMakeLists.txt to build MOM6.
3. PR in GEOSgcm to uptick MOM6 version number
4. Also for @sanAkel, all configs of MOM6 for GEOS need to be updated/sync'ed in with the right defaults.

@mathomp4 heads up: for known reasons (bugfixes and improvements: changes in default values of parameters, see mom-ocean/MOM6#1556) this code will be non-zero difference (from the way we currently run). Affects only the MOM6 based GEOS AOGCM. I would certainly need your help with above 1 (maybe!) and 3 certainly! 🙏

[mathomp4]

@sanAkel I suppose there is also step 0:

0. Pull in latest dev/gfdl to GEOS-ESM fork of MOM6 😄

[mathomp4]

@sanAkel @sdrabenh Has moved Ocean to the separate repo. This PR needs to be re-done there.

[sanAkel]

Will do. Thanks!

[sanAkel]

This PR now moves to GEOS-ESM/GEOS_OceanGridComp/ hence closing here.