Update test fixture after change in S3 bucket permissions

[edmorley]

S3 directory listing permissions were removed from the buildpack's S3 bucket, which means non-existent files now return 403 rather than 404.

The implementation for error handling already works with both:

heroku-buildpack-python/lib/python.sh

Lines 74 to 76 in 855d7e6

	# We have to check for HTTP 403s too, since S3 will return a 403 instead of a 404 for
	# missing files, if the S3 bucket does not have public list permissions enabled.
	if [[ "${python_full_version}" != "${latest_known_patch_version}" ]] && grep --quiet "The requested URL returned error: 40[34]" "${error_log}"; then

However, the test assertion needs to be loosened to resolve this CI failure:
https://github.com/heroku/heroku-buildpack-python/actions/runs/22640940619/job/65680836050#step:5:497

GUS-W-21443369.