Fix test to not save two geotiffs with the same name

[djhoese]

Windows started failing in CI because this test was trying to save 2 DataArrays to the same output filename. That is not a use case we want to support, but I think was done accidentally as the test class evolved. This PR updates the test to be explicit about what dataset is being saved and Windows CI passes now.

• Closes #xxxx
• Tests added
• Fully documented
• Add your name to AUTHORS.md if not there already

[pnuu]

To be more specific, we don't want to support saving two datasets to one image file. Saving to NetCDF4 is a valid usecase.

[pnuu]

Zenodo is again acting up, I restarted the tests.

[pnuu]

Another restart, same reason.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.31%. Comparing base (2554db5) to head (714e018).
⚠️ Report is 26 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3318      +/-   ##
==========================================
- Coverage   96.34%   96.31%   -0.03%     
==========================================
  Files         463      463              
  Lines       58916    58916              
==========================================
- Hits        56760    56745      -15     
- Misses       2156     2171      +15     

Flag	Coverage Δ
behaviourtests	3.58% <0.00%> (-0.02%)	⬇️
unittests	96.40% <100.00%> (-0.03%)	⬇️

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