GEOS-Chem submod update: Read Hg restarts from v2023-12 folder

This commit informs the GCClassic superproject about the following
commits that were pushed to the GitHub geoschem/geos-chem repository:

c98fcce0a Merge PR #2059 (Now read Hg restarts from v2023-12 folder)

This adds an update for the Hg simulation to use well-spun-up initial
conditions from ExtData/GEOSCHEM_RESTARTS/v2023-12.

Signed-off-by: Bob Yantosca <[email protected]>