`np.mat` removed in NumPy 2.0+

[mahamat9]

The use of np.mat in nimfa causes an AttributeError when using NumPy 2.0 or later, as np.mat has been removed. This issue occurs in the following files:

• nimfa/methods/seeding/nndsvd.py
• nimfa/utils/linalg.py

Steps to reproduce:

Install NumPy 2.0 or later.
Run any code that uses nimfa, such as NMF initialization with Nndsvd.

Error message:

AttributeError: np.mat was removed in the NumPy 2.0 release. Use np.asmatrix instead.

one solution:
Replace all occurrences of np.mat with np.asmatrix in the code source. This change resolves the issue and maintains compatibility with both older and newer versions of NumPy.