Remove star import in jmetal.lab.statistical_test.functions

[rnestler]

This helps with statical analysis tools like mypy or flake8.

[rnestler]

Ah I just noticed that this project uses git-flow workflow with develop as the development branch. I'll rebase this on develop and change the target branch.

Is there any reason that develop isn't the default branch? This would help a lot when contributing first to the project, since it will be visible directly that development should happen there.