gh-406: support newer scipy versions

[ntessore]

Add support for newer scipy versions by importing scipy.special.legendre_p_all() as a drop-in replacement of the deprecated lpn.

Closes: #406

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Flag	Coverage Δ
py3.10	83.38% <37.50%> (-0.15%)	⬇️
py3.11	83.38% <37.50%> (-0.15%)	⬇️
py3.12	83.34% <37.50%> (-0.15%)	⬇️
py3.13	82.91% <37.50%> (-0.15%)	⬇️
py3.9	83.58% <100.00%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
heracles/transforms.py	87.50% <100.00%> (+0.46%)	⬆️

🚀 New features to boost your workflow:

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

[JaimeRZP]

All good!

[ntessore]

Oh, this fails in the last supported scipy for Python 3.9, which is what we need for SGS support. Let me change the PR to support both.