setup.cfg: remove redundant packages/py_modules

The `package_dir` already achieves this.

Author: bluetech

setup.cfg

@@ -33,16 +33,6 @@ project_urls =
     Tracker=https://github.com/pytest-dev/pytest/issues
 
 [options]
-packages =
-    _pytest
-    _pytest._code
-    _pytest._io
-    _pytest._py
-    _pytest.assertion
-    _pytest.config
-    _pytest.mark
-    pytest
-py_modules = py
 install_requires =
     iniconfig
     packaging