update setup.py by being explicit on the minimum numpy version needed to avoid...

update setup.py by being explicit on the minimum numpy version needed to avoid ABI incompatibilities.

Example of error if pyfaust is compiled with numpy 1.20 but used with numpy 1.19:

import pyfaust gives:
ValueError: numpy.ndarray size changed, may indicate binary incompatibility. Expected 88 from C header, got 80 from PyObject

wrapper/python/setup.py.in

@@ -50,7 +50,7 @@ setup(
     classifiers = [ 'License :: OSI Approved :: BSD License',
                    'Programming Language :: Python :: 3',
                   '@GPU_CUDA_VERSION_PYPI_CLASSIFIER@'],
-    install_requires = [ 'pygsp', 'scipy', 'numpy', 'matplotlib>=2.0.0',
+    install_requires = [ 'pygsp', 'scipy', 'numpy>=1.20', 'matplotlib>=2.0.0',
                         'pathlib'], #ENOTE: order matters (last pkg installed first)
     license = "3-clause BSD 2.0",
     package_data = {