Deprecation of `interp2d`

[JannisNe]

Lately seeing this deprecation warning:

DeprecationWarning: interp2d is deprecated in SciPy 1.10 and will be removed in SciPy 1.14.0.

For legacy code, nearly bug-for-bug compatible replacements are
RectBivariateSpline on regular grids, and bisplrep/bisplev for
scattered 2D data.

In new code, for regular grids use RegularGridInterpolator instead.
For scattered data, prefer LinearNDInterpolator or
CloughTocher2DInterpolator.

For more details see
https://scipy.github.io/devdocs/notebooks/interp_transition_guide.html

This affects StandardLLH.create_acceptance_function(). SHould be replaced as suggested in the warning.

[mlincett]

Ehe, this is there since #270

I assume replacing with RectBivariateSpline should be painless.

[JannisNe]

Ok, then closing because duplicate of #270