6.4.0 conflicts with `roave/security-advisories`

[wutsch0]

Version 6.4.0 of friendsofsymfony1/swiftmailer conflicts with the current version of https://github.com/Roave/SecurityAdvisories.

As friendsofsymfony1/swiftmailer itself is not part of the conflicts list, its likely because of roave/security-advisories conflicting with "swiftmailer/swiftmailer": "<6.2.5", and friendsofsymfony1/swiftmailer replaces all versions ^6, including version 6.0.0 - 6.2.4

[thePanz]

Fixed by #25