Bug 7143: update the es-ES translation attribution as of 3.12 onwards

Bug 7143: update the es-ES translation attribution as of 3.12 onwards

The currently maintained stable releases translations are/were done by
the following individuals and it should be acknowledged in the about page.

This patch also removes the venezuelian spanish translation, that was removed
long time ago.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>