Changes for scipy 1.11.x

[torressa]

Related to #121 scipy >=1.11 has changed the behavior from the release notes:

A new public base class scipy.sparse.sparray was introduced, allowing further extension of the sparse array API (such as the support for 1-dimensional sparse arrays) without breaking backwards compatibility. isinstance(x, scipy.sparse.sparray) to select the new sparse array classes, while isinstance(x, scipy.sparse.spmatrix) selects only the old sparse matrix classes.

This got missed in the actions for #121 (and every commit since) as the Python version used there was 3.8 for which scipy 1.11.x has no wheel!

@simonbowly This is probably not the correct fix so please take a look.

[simonbowly]

Oversight on my part sorry. I don't think the test really needed to be this strict; a better way to do the return type check is with sp.issparse. This recognises both matrices and arrays and has stayed consistent across scipy versions, so we can leave the requirements as is. I updated that with #126, so I'll close this PR.

[torressa]

Thanks Simon!