Tmp restrict SciPy

• Maintenance:

  • Restricting to SciPy<1.15. The function scipy.interpolate.interpnd is deprecated, and scipy.interpolate.interpnd._ndim_coords_from_array was removed. Needs fixing in emg3d.maps._points_from_grids.
  • Re-adding a test for normalizing source warning; avoid rounding over and over again in recursion of creating a dipole/wire source.