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

src/Model/Conversation.php

@@ -4,8 +4,8 @@
  */
 namespace Friendica\Model;
 
+use Friendica\Database\dba;
 use Friendica\Database\DBM;
-use dba;
 
 require_once "include/dba.php";