Don't release the printer after using it to change a property

The printer should not be released after changing a property on it as it
is still needed by QPrinter elsewhere. It is released as appropriate
automatically already.

Task-number: QTBUG-32831

Change-Id: Idb2d98b25b62f343015a0a0fb3c9a0d506546132
Reviewed-by: Liang Qi <liang.qi@digia.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>