MAI: call `networkx.from_numpy_array`, instead of `from_numpy_matrix`
MAI: call `networkx.from_numpy_array`, instead of `from_numpy_matrix`

because the function `networkx.from_numpy_matrix` has been deprecated
in `networkx >= 2.6` (under development) [commit][1]. As recommended by the
deprecation message of `networkx`, use instead the function
`networkx.from_numpy_array`.

The function `networkx.from_numpy_array` [takes a 2-dimensional
`numpy.ndarray`][2]. The variable `datatemp` is of type
[`numpy.recarray`][3], because the function [`scipy.io.loadmat`][4]
returns by default a `dict` with values of type `numpy.recarray`.

The following code works as expected:

```python
import networkx as nx
import numpy as np

a = np.ndarray([[0, 1], [0.2, 3]])
b = a.view(np.recarray)
assert isinstance(b, np.recarray), type(b)
g = nx.from_numpy_array(b)
```

So the variable `datatemp` can be directly passed to the
function `networkx.from_numpy_array`. Moreover, the variable `A`
can then be removed, because it is not used elsewhere.

[1]: https://github.com/networkx/networkx/commit/ddf707dc0c35edf5bda884de8534899af945ad78
[2]: https://networkx.org/documentation/latest/reference/generated/networkx.convert_matrix.from_numpy_array.html
[3]: https://numpy.org/doc/stable/reference/generated/numpy.recarray.html
[4]: https://docs.scipy.org/doc/scipy/reference/generated/scipy.io.loadmat.html

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