Remove warning configuration that promotes SAWarning to error

[rsyring]

https://github.com/level12/keg-app-cookiecutter/blob/d6de510da46631320627148abaa43dc1d62f3c22/%7B%7Bcookiecutter.src_dirname%7D%7D/%7B%7Bcookiecutter.project_pymod%7D%7D/__init__.py#L6

Since pytest.ini now sets all warnings as errors, this is no longer needed.