GEOS-Chem submod update: Merge PR #2413 (Fix unit conv in aerosol sim)

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

cd3857ade Merge PR #2413 (Fix unit conversion in aerosol-only sim)

This PR fixes a longstanding unit conversion issue in the
aerosol-only simulation.

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