Bug#1095356: mdp: FTBFS: E AttributeError: `np.longfloat` was removed in the NumPy 2.0 release.

[Santiago Vila]

Note: This is very similar to #1095026 and I would have skipped it if UDD
had told me it was a ftbfs bug affecting the unstable version, but version
tracking seems not to be working here and I don't know why.

Thanks.