remove documentation about setuptools integration Refs #5534
remove documentation about setuptools integration Refs #5534

integrating with `python setup.py test` is not good practice!
RonnyPfannschmidt/pytest,tomviner/pytest,The-Compiler/pytest,pytest-dev/pytest,Akasurde/pytest,nicoddemus/pytest,markshao/pytest,alfredodeza/pytest,nicoddemus/pytest,tomviner/pytest,The-Compiler/pytest