Remove functions from sobol_seq.py

[alchemyst]

There are functions in sobol_seq.py which are not used.

• is_prime() is only used in prime_ge, which is not used anywhere else.
• i4_uniform() is not used anywhere else

The less code we have, the less we need to maintain.

[Stefan-Endres]

I was getting some strange import errors when I tried to run the unittests where it's searching for a missing attribute of the module even though we just import everything with *. I've changed the way these functions functions are imported and removed these functions in dcbf6f9491b3fbf8584fc4acba2c98628c2e62b0.

[alchemyst]

I think the issue is that you didn't remove the functions from the __all__ for the module.

[alchemyst]

I've removed one more function and updated __all__ in de59e0d0df1e70b07b7efefad891492e181cae54

[Stefan-Endres]

Ah, thank you!