replace use of np.array(copy=False) with np.asarray()

[owenclaxton-SMC]

From the author's textbook, several cells fail. Example:

import kf_book.mkf_internal as mkf_internal

mean = [2., 17.]
cov = [[10., 0.], 
       [0., 4.]]

mkf_internal.plot_3d_covariance(mean, cov)

Yields:

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
...
ValueError: Unable to avoid copy while creating an array as requested.
If using `np.array(obj, copy=False)` replace it with `np.asarray(obj)` to allow a copy when needed (no behavior change in NumPy 1.x).
For more details, see https://numpy.org/devdocs/numpy_2_0_migration_guide.html#adapting-to-changes-in-the-copy-keyword.

This pull request applies this change to this function, noting the change may still be required elsewhere.