Use a better OlderThan for DeleteInactiveUsers (#19693)

* Use a better OlderThan for DeleteInactiveUsers

- Currently the OlderThan is zero, for instances that enable or run this
task this could actually delete just new users that still need to
confirm their email. This patch fixes that by setting the default to the
`ActiveCodeLives` setting, which corresponds to the amount of time that
a user can active their account, thus avoiding the issue of deleting
unactivated email users.

* Use correct duration

services/cron/tasks_extended.go

 			RunAtStart: false,
 			Schedule:   "@annually",
 		},
-		OlderThan: 0 * time.Second,
+		OlderThan: time.Minute * time.Duration(setting.Service.ActiveCodeLives),
 	}, func(ctx context.Context, _ *user_model.User, config Config) error {
 		olderThanConfig := config.(*OlderThanConfig)
 		return user_service.DeleteInactiveUsers(ctx, olderThanConfig.OlderThan)