Modify from_legacy_anndata so that it can read older ST datasets

[timtreis]

No description provided.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 10.25641% with 35 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.23%. Comparing base (28d05a2) to head (6080158).

Files with missing lines	Patch %	Lines
src/spatialdata_io/converters/legacy_anndata.py	10.25%	35 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #347      +/-   ##
==========================================
- Coverage   55.25%   55.23%   -0.03%     
==========================================
  Files          26       26              
  Lines        2843     2848       +5     
==========================================
+ Hits         1571     1573       +2     
- Misses       1272     1275       +3     

Files with missing lines	Coverage Δ
src/spatialdata_io/converters/legacy_anndata.py	51.36% <10.25%> (-0.41%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[LucaMarconato]

Thanks @timtreis.

I changed one comment to match the order of some operations in the code. I also moved one logger.warning() to logger.debug() as one of the log was not a warning and I didn't want to print messages by default (logger.info()).