External Libraries: Upgrade PHPMailer to version 6.9.2.
This is a maintenance release with minor bug fixes.
References:
* [https://github.com/PHPMailer/PHPMailer/releases/tag/v6.9.2 PHPMailer 6.9.2 release notes]
* [https://github.com/PHPMailer/PHPMailer/compare/v6.9.1...v6.9.2 Full list of changes in PHPMailer 6.9.2]
Follow-up to [50628], [50799], [51169], [51634], [51635], [52252], [52749], [52811], [53500], [53535], [53917], [54427], [54937], [55557], [56484], [57137].
Props ayeshrajans.
Fixes #62206.
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