Remove transactional function call

PHP 5.3 complains about $this outside an object.
They are not needed, because the _addIdx method also executes a
query against the same database. It is covered by the transaction
automatically.
Feature from gihp@0.10.0 is required to work

gihp\Metadata\Person::parse() is called by the code.
It was only added in gihp@0.10.0