Improve stubsabot logic for finding the first release with a py.typed file (#9600)

Author: AlexWaygood

scripts/stubsabot.py

@@ -173,7 +173,8 @@ async def release_contains_py_typed(release_to_download: PypiReleaseDownload, *,
 async def find_first_release_with_py_typed(pypi_info: PypiInfo, *, session: aiohttp.ClientSession) -> PypiReleaseDownload:
     release_iter = pypi_info.releases_in_descending_order()
     while await release_contains_py_typed(release := next(release_iter), session=session):
-        first_release_with_py_typed = release
+        if not release.version.is_prerelease:
+            first_release_with_py_typed = release
     return first_release_with_py_typed