External Libraries: Update the SimplePie library to version 1.5.7.
This version shows significant improvements in the compatibility of SimplePie with PHP 8.0, 8.1, and even contains an initial PHP 8.2 fix. The release also contains a number of other bug fixes.
Release notes: https://github.com/simplepie/simplepie/releases/tag/1.5.7
For a full list of changes in this update, see the SimplePie GitHub:
https://github.com/simplepie/simplepie/compare/1.5.6...1.5.7
Follow-up to [47733], [49176].
Props jrf, SergeyBiryukov.
Fixes #54659.
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