build: remove unused setuptools setting

This change removes `options.package_data` from `setup.cfg`.

`options.package_data` is used by setuptools
[[ref](https://setuptools.pypa.io/en/latest/userguide/datafiles.html#package-data)].
RDFLib, however, no longer uses setuptools and uses poetry instead, so
it has no effect, and poetry does include all files in the package by
default.

setup.cfg

@@ -1,6 +1,3 @@
-[options.package_data]
-rdflib = py.typed
-
 # https://flake8.pycqa.org/en/latest/user/configuration.html
 [flake8]
 exclude =