Bump phpmailer/phpmailer from 6.1.4 to 6.1.5

Bumps [phpmailer/phpmailer](https://github.com/PHPMailer/PHPMailer) from 6.1.4 to 6.1.5.
- [Release notes](https://github.com/PHPMailer/PHPMailer/releases)
- [Changelog](https://github.com/PHPMailer/PHPMailer/blob/master/changelog.md)
- [Commits](PHPMailer/PHPMailer@v6.1.4...v6.1.5)

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Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Fixes #26784
PR #1631