fix: replace removed np.trapz and np.bool APIs

[xyf5432]

Fixes #11

Problem

Two removed numpy APIs are used in this repo:

• np.trapz — removed in numpy 2.4.0 → AttributeError: module 'numpy' has no attribute 'trapz' on modern numpy
• np.bool — removed in numpy 1.24.0 → AttributeError: module 'numpy' has no attribute 'bool' on numpy >= 1.24

Fix

• For np.trapz: add a compat shim in ana/ckn.py and ana/trapz.py that prefers numpy.trapezoid (available since numpy 2.0, identical signature) and falls back to numpy.trapz on numpy < 2.0, so the scripts keep working on every numpy version:

try:
    from numpy import trapezoid as _trapz_impl
except ImportError:
    from numpy import trapz as _trapz_impl

• For np.bool: use the builtin bool, which numpy accepts as a dtype with identical behavior.
• Docstring reference, doc URL, and the figure title in ana/trapz.py are updated to the new API name.

Verification

• np.trapezoid(y, x=None, dx=1.0, axis=-1) has an identical signature to trapz
• dtype=bool produces identical boolean arrays
• Verified the shim on numpy 1.26.4 (numpy<2 branch): it selects trapz and computes the expected trapezoidal integral
• Similar fixes in other downstream projects: gpytorch#2695