python-rdflib fails to build with sphinx 8.x in Fedora 42 (currently Rawhide).

The issue detected:
```
reading sources... [ 17%] apidocs/rdflib.namespace
WARNING: Cannot resolve forward reference in type annotations of "rdflib.query.Result.__iter__": name '_SubjectType' is not defined

Exception occurred:
  File "/usr/lib/python3.13/site-packages/sphinx/util/inspect.py", line 485, in object_description
    raise ValueError from exc
ValueError
```

Please work with upstream on this issue, I plan to ship sphinx 8 in two weeks.


For the logs from testing build attempts, see:
https://copr.fedorainfracloud.org/coprs/thrnciar/python-sphinx/package/python-rdflib/

You can test you package in mock running:

$ mock -r fedora-rawhide-x86_64
--addrepo=https://download.copr.fedorainfracloud.org/results/thrnciar/python-sphinx/fedora-rawhide-x86_64/ --no-clean your.src.rpm
$ mock -r fedora-rawhide-x86_64
--addrepo=https://download.copr.fedorainfracloud.org/results/thrnciar/python-sphinx/fedora-rawhide-x86_64/ shell

We'd like to include Sphinx 8 in Fedora 42.
Let us know here if you have any questions. Thank you!