Fallback to Spanish rather than Portuguese

Sorry, I didn't noticed that coment because I didn't watch pages at this wiki.

It could be good to fallback messages to spanish because all people at Galicia knows spanish, but in the other hand, in my work here at translatewiki, I have found that there are more messages translated to portuguese than to spanish, and with a greater quality. For this reason, I think that it could be more useful for galician users keep the fallback to portuguese. Bye.