Swap default page title for Special:BlankPage in Spanish

Swap default page title for Special:BlankPage in Spanish

"Blanquear página" is a wrong translation in this context.
"Blanquear" is using "blank" as the verb and means "to blank a page",
but this page should translate "blank" as an adjective "this page is blank"

This was already in the list of aliases so I've swapped them so the correct
one is first and is picked as the default page name in wikis with Spanish
content language.

Change-Id: I29c2b02937878c09df09460eedbc5df697e51e34