Update config schema for Symfony 7.3 mailer security improvements

Looks good to me.

I assume retry_period from the changelog is not relevant to us?

I assume retry_period from the changelog is not relevant to us?

No. Its injected into RoundRobinTransport if the DSN is parsed from a string. Since we are using ✨ Use structured DSN instead of URI in system.mail mailer_dsn Fixed , this isn't in the code path.