[3.9] Fix tests for XMLPullParser with Expat 2.6.0 (GH-115133) by sethmlarson · Pull Request #115535 · python/cpython

@serhiy-storchaka @sethmlarson

…ythonGH-115164)

Feeding the parser by too small chunks defers parsing to prevent
CVE-2023-52425. Future versions of Expat may be more reactive.
(cherry picked from commit 4a08e7b)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>