Pontoon: Updated Spanish (es-MX) localization of Pontoon Intro
Pontoon: Updated Spanish (es-MX) localization of Pontoon Intro

Translation authors:
- Mauricio Navarro Miranda <mautematico@mozilla-mexico.org>

mathjazz/pontoon-intro,mathjazz/pontoon-intro,jotes/pontoon-intro,jotes/pontoon-intro,jotes/pontoon-intro,mathjazz/pontoon-intro