Deprecate gx1 CORE forcing option

[apcraig]

PR checklist

• Short (1 sentence) summary of your PR:
  Deprecate gx1 CORE forcing option
• Developer(s):
  apcraig
• Suggest PR reviewers from list in the column to the right.
• Please copy the PR test results link or provide a summary of testing completed below.
  Ran the quick suite on cheyenne on 3 compilers as well as the full test suite on cheyenne with the gnu compiler. Everything passes and is bit-for-bit. https://github.com/CICE-Consortium/Test-Results/wiki/cice_by_hash_forks#9e4d244d7feb6ad9d03cc488c34c1f22c4ea7612
• How much do the PR code changes differ from the unmodified code?
  • bit for bit
  • different at roundoff level
  • more substantial
• Does this PR create or have dependencies on Icepack or any other models?
  • Yes
  • No
• Does this PR add any new test cases?
  • Yes
  • No
• Is the documentation being updated? ("Documentation" includes information on the wiki or in the .rst files from doc/source/, which are used to create the online technical docs at https://readthedocs.org/projects/cice-consortium-cice/. A test build of the technical docs will be performed as part of the PR testing.)
  • Yes
  • No, does the documentation need to be updated at a later time?
    • Yes
    • No
• Please provide any additional information or relevant details below:

The gx1 CORE forcing uses the LYq forcing option and the LYq option is being removed. Deprecated source code by adding temporary cpp (UNDEPRECATE_LYq). The code can be formally removed later. Removed the LYq documentation. Removed the set_nml file and removed one test case.

Closes #627.

[dabail10]

Looks good.

[eclare108213]

This looks fine to me too. The forcing wiki page likely will need to be updated -- could include a note that the LYq option / CORE forcing was deprecated -- and I can also add that information to the zenodo metadata.

[rallard77]

Thanks for doing this Tony!

[apcraig]

I have updated the forcing wiki page to indicate that the gx1 core forcing was deprecated on 10/2021 and is available up to CICE6.3.0. At present, the data is still available on zenodo. We should probably remove it the next time we create a gx1 tar file. Users of older CICE versions can download earlier versions of the input data.