Bump phpmailer/phpmailer from 5.2.23 to 6.1.6 in /SustProject_main

Bumps [phpmailer/phpmailer](https://github.com/PHPMailer/PHPMailer) from 5.2.23 to 6.1.6.
- [Release notes](https://github.com/PHPMailer/PHPMailer/releases)
- [Changelog](https://github.com/PHPMailer/PHPMailer/blob/master/changelog.md)
- [Commits](PHPMailer/PHPMailer@v5.2.23...v6.1.6)

---
updated-dependencies:
- dependency-name: phpmailer/phpmailer
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

SustProject_main/composer.json

@@ -1,7 +1,7 @@
 {
 
   "require": {
-    "phpmailer/phpmailer": "v5.2.23"
+    "phpmailer/phpmailer": "v6.1.6"
   }