fix(deps): update module github.com/wneessen/go-mail to v0.3.5 (#1325)

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/1325
Co-authored-by: renovate <renovatebot@kolaente.de>
Co-committed-by: renovate <renovatebot@kolaente.de>

pkg/mail/send_mail.go

@@ -85,7 +85,7 @@ func getMessage(opts *Opts) *mail.Msg {
 	m.Subject(opts.Subject)
 
 	for _, h := range opts.Headers {
-		m.SetHeader(h.Field, h.Content)
+		m.SetGenHeader(h.Field, h.Content)
 	}
 
 	for name, content := range opts.Embeds {