ombg, oman, innov1, innov2, etc

[guoqing-noaa]

@Junjun-NOAA @spanNOAA and I did experiments and confirmed that:
since this PR https://github.com/JCSDA-internal/oops/pull/2749 which was merged on Sept 24th,
ombg always refers to the O-B before any outerloops
oman always refers to the O-A after all outerloops
innov1 always refers to the O-F after the 1st outerloop and before the 2nd outerloop
innov2 always refers to the O-F after the 2nd outerloop and before the 3rd outerloop
....

These diagnostics are always generated in the latest RDASApp and we no longer need to specify the diagnostics.departures keys in the yaml file.
i.e. let's remove the following lines in our RDASApp yaml files.

diagnostics:
  departures: ombg

Here is a snapshot of the relevant codes:
JCSDA/oops@f099b35#diff-6f90c48cceb31841da068f513e80c30efb49d27800cd1d0ac988931f8a62e37fL210

I have tested the new yaml file without the diagnostics.departures keys and it worked as expected.
Here is my test directory and yaml file:
/scratch1/BMC/wrfruc/gge/RDASApp/expr/mpas_2024052700_save/rrfs_mpasjedi_2024052700_Ens3Dvar.yaml
and the jdiag file:
/scratch1/BMC/wrfruc/gge/RDASApp/expr/mpas_2024052700_save/jdiag.nc4

Tag @HaidaoLin-NOAA @SamuelDegelia-NOAA as this also addresses issue #229

[guoqing-noaa]

Based on the above code change, I did tests and also confirmed that we can remove this section and still get the oman in the jdiag files.

final:
  diagnostics:
    departures: oman

[guoqing-noaa]

Also for information, RDASApp included the aforementioned OOPS PR https://github.com/JCSDA-internal/oops/pull/2749 since Nov. 6th through Sam's PR #217 which updated OOPS from d7721732 (Aug 29, 2024, OOPS PR #2719) to b2e6d273 (Oct 22, 2024, OOPS PR #2760)