Simplify Mozilla specific code by using en-US repo
Simplify Mozilla specific code by using en-US repo

No need to clone entire Mozilla source code and extract l10n files.

vivekanand1101/pontoon,jotes/pontoon,sudheesh001/pontoon,mastizada/pontoon,mathjazz/pontoon,vivekanand1101/pontoon,m8ttyB/pontoon,participedia/pontoon,yfdyh000/pontoon,mastizada/pontoon,mozilla/pontoon,participedia/pontoon,mozilla/pontoon,mathjazz/pontoon,Osmose/pontoon,Osmose/pontoon,m8ttyB/pontoon,mastizada/pontoon,jotes/pontoon,jotes/pontoon,participedia/pontoon,sudheesh001/pontoon,yfdyh000/pontoon,jotes/pontoon,Osmose/pontoon,vivekanand1101/pontoon,m8ttyB/pontoon,mastizada/pontoon,mozilla/pontoon,mozilla/pontoon,sudheesh001/pontoon,participedia/pontoon,Osmose/pontoon,mathjazz/pontoon,yfdyh000/pontoon,mathjazz/pontoon,m8ttyB/pontoon,mathjazz/pontoon,sudheesh001/pontoon,mozilla/pontoon,yfdyh000/pontoon,vivekanand1101/pontoon