Update some deprecated uses of libraries

[coveralls]

Coverage increased (+0.02%) to 88.618% when pulling a38b41b84652d925deb6d94e9f42494cd90ddf68 on deprecations into 7b87faec7fc6f2d6ee88a0090a622968ab26d9a9 on master.

[mdeff]

We want to initialize the pseudo-random number generator with a seed (i.e., do default_rng(seed) instead of default_rng()) to get reproducible results (e.g., when we instantiate a random graph then check its properties).

Whether seed is 42, 1, or anything usually doesn't matter much. But sometimes we might prefer a random draw over another (e.g., a seed that generates a connected graph over a disconnected one).

[nperraud]

Approved. You can merge.

Thanks a lot

[mdeff]

Thank you!