Update use statement lists with new Friendica\Database\dba class

- Remove unused use statement
- Remove superfluous use statements (classes in the same namespace)
- Add missing use statements

mod/dfrn_poll.php

@@ -3,10 +3,12 @@
 /**
  * @file mod/dfrn_poll.php
  */
+
 use Friendica\App;
 use Friendica\Core\Config;
 use Friendica\Core\L10n;
 use Friendica\Core\System;
+use Friendica\Database\dba;
 use Friendica\Database\DBM;
 use Friendica\Module\Login;
 use Friendica\Protocol\DFRN;