GEOS-Chem submod update: Merge PR #2397 (Global 0.5 deg TransportTrac…

…ers runs)

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

07884955e Merge PR #2397 (Add GCC global TransportTracer 0.5 degree run w/ GEOS-IT)

This PR updates the GC-Classic create run directory script. It now offers
the option of a global 1/2-degree run using the transport tracer simulation
with GEOS-IT meteorology fields.

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