fix: dotplot scaling with swapped axes

[ilan-gold]

Despite the title of the corresponding issue, I took

at first I thought it was a matter of using standard_scale="group"

to mean that scaling was not the problem.

But it turns that that is indeed broken and actually both scaling methods were broken with swapped axes for a very explainable reason - the scaling operation was happening on the wrong axis when the axis was swapped because it was fixed. Group scaling always happened on axis 0, for example, even though the group could be on axis 1 when the axes are swapped.

If you run the test suite on main without the changes, there should be errors for only the two swapped axes tests. Arguably the tests should be pared down, but parametrizing is free and easy. Happy to remove the extra ones.

• Closes Dotplot scaling with swapped axes #3708
• Tests included or not required because:

• Release notes not necessary because:

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.57%. Comparing base (ae93ac7) to head (3496f18).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3851   +/-   ##
=======================================
  Coverage   76.56%   76.57%           
=======================================
  Files         115      115           
  Lines       12402    12406    +4     
=======================================
+ Hits         9496     9500    +4     
  Misses       2906     2906           

Files with missing lines	Coverage Δ
src/scanpy/plotting/_dotplot.py	93.48% <100.00%> (+0.10%)	⬆️

[flying-sheep]

lovely!