Sarina/fix underscore resource

@singingwolfboy @louyihua this is necessary for the transifex pull commands to work.


Yep, so this resource doesn't exist when we go to merge, so `python i18n/generate.py --strict` fails.

We really should only be uploading `underscore-studio.po` to Transifex as we don't have any Underscore templates in the LMS, IIRC. @singingwolfboy is working on figuring that out right now and will update this PR when he's figured it out.