Remove useless default SQL columns

app/classes/Framadate/Migration/From_0_0_to_0_8_Migration.php

@@ -72,7 +72,7 @@ CREATE TABLE IF NOT EXISTS `sondage` (
   `titre` text,
   `id_sondage_admin` char(24) DEFAULT NULL,
   `date_creation` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
-  `date_fin` timestamp NOT NULL DEFAULT \'0000-00-00 00:00:00\',
+  `date_fin` timestamp NOT NULL,
   `format` varchar(2) DEFAULT NULL,
   `mailsonde` tinyint(1) DEFAULT \'0\',
   `statut` int(11) NOT NULL DEFAULT \'1\' COMMENT \'1 = actif ; 0 = inactif ; \',

app/classes/Framadate/Migration/From_0_8_to_0_9_Migration.php

@@ -90,7 +90,7 @@ CREATE TABLE IF NOT EXISTS `' . Utils::table('poll') . '` (
   `admin_name`      VARCHAR(64) DEFAULT NULL,
   `admin_mail`      VARCHAR(128) DEFAULT NULL,
   `creation_date`   TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
-  `end_date`        TIMESTAMP NOT NULL DEFAULT \'0000-00-00 00:00:00\',
+  `end_date`        TIMESTAMP NOT NULL,
   `format`          VARCHAR(1) DEFAULT NULL,
   `editable`        TINYINT(1) DEFAULT \'0\',
   `receiveNewVotes` TINYINT(1) DEFAULT \'0\',