Stop converting package_data to extra_files in pysetup create (#13712).

pysetup create, the setup.cfg creation helper, used to convert
package_data (from an existing setup.py) into extra_files, the
replacement for MANIFEST.in, but these files are only present in sdists,
not installed: they don’t have the same use case at all, so converting
one into the other did not work.
3 files changed