Update workaround for #145

[khaeru]

The regression is still present in xarray 2024.11.0, so relax the mark condition to apply to versions equal to or greater than 2024.10.0.

PR checklist

• Checks all ✅
• Update documentation N/A, test changes only
• Update doc/whatsnew.rst

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.85%. Comparing base (b6d92e1) to head (e7d3254).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #154   +/-   ##
=======================================
  Coverage   99.85%   99.85%           
=======================================
  Files          52       52           
  Lines        4705     4705           
=======================================
  Hits         4698     4698           
  Misses          7        7           

Files with missing lines	Coverage Δ
genno/testing/__init__.py	100.00% <ø> (ø)