Update the calls to be compatible with NumPy 2.0

[mplzik]

With the release of NumPy 2.0, the ptp method was removed, with a replacement being np.ptp.

See also: https://numpy.org/devdocs/numpy_2_0_migration_guide.html#ndarray-and-scalar-methods

Signed-off-by: Milan Plzik [email protected]