Remove useless constant

Author: SamuelTallet

config.php

@@ -27,10 +27,3 @@
  * @var string
  */
 define('MPG_MONGODB_PORT', '27017');
-
-/**
- * MongoDB server database.
- * 
- * @var string
- */
-define('MPG_MONGODB_DATABASE', '');

src/Helpers/MongoDBHelper.php

@@ -25,10 +25,6 @@ public static function createClient() : MongoDBClient {
             $clientUri .= ':' . MPG_MONGODB_PORT;
         }
 
-        if ( !empty(MPG_MONGODB_DATABASE) ) {
-            $clientUri .= '/' . MPG_MONGODB_DATABASE;
-        }
-
         return new MongoDBClient($clientUri);
 
     }