fix SciPy matrix for API change

This patch changes the argument for cg, gmres, etc. from tol= to rtol= if SciPy
is newer than version 1.12.
https://docs.scipy.org/doc/scipy-1.12.0/release/1.12.0-notes.html#deprecated-features

nutils/matrix/_scipy.py

@@ -82,7 +82,8 @@ def mycallback(arg):
                 if callback:
                     callback(res)
                 reformat(100 * numpy.log10(max(atol, res)) / numpy.log10(atol))
-            lhs, status = solverfun(self.core, rhs, M=precon, tol=0., atol=atol, callback=mycallback, **solverargs)
+            solverargs['rtol' if scipy.version.version >= '1.12.0' else 'tol'] = 0. # relative tolerance is already factored into atol
+            lhs, status = solverfun(self.core, rhs, M=precon, atol=atol, callback=mycallback, **solverargs)
         if status != 0:
             raise Exception('status {}'.format(status))
         return lhs