fixed miss method and return type error

[vtumi]

use the table_prefix option, i found an error.

$table = $this->table('user');
$table->truncate();

PHP Fatal error: Uncaught Error: Cannot call abstract method Phinx\Db\Adapter\AdapterInterface::truncateTable()

[yashtodi94]

Please do provide a description for the pull request.

[robmorgan]

thanks!