Fix barotropic streamfuncion

[xylar]

Without this fix, we were seeing:

  File "/gpfs/fs1/home/ac.xylar/mpas_work/MPAS-Analysis/add_OSNAP_TSclimtransects/mpas_analysis/shared/plot/climatology_map.py", line 615, in plot_panel
    for collection in cs.collections:
                      ^^^^^^^^^^^^^^
AttributeError: 'GeoContourSet' object has no attribute 'collections'

in the logs for barotropic streamfuncion plot tasks.

Checklist

• Testing comment in the PR documents testing used to verify the changes

[xylar]

Testing

I ran the test suite on Chrysalis. I didn't check all test results but the main test passes, whereas it was crashing with the error message above before. BSF plots look like normal:
https://web.lcrc.anl.gov/public/e3sm/diagnostic_output/ac.xasay-davis/analysis_testing/chrysalis/fix-bsf-plots/main_py3.11/ocean/barotropicStreamfunction_antarctic_extended_main_py3.11_ANN_years0003-0010.png