OSS: Marked strings.xml as non-translatable and removed irrelevant translations

Summary: These strings shouldn't be translated by FB system because each app has its own set of languages and/or translation outputs. We're keeping just values/strings.xml in the repo.

Reviewed By: cpojer

Differential Revision: D15087192

fbshipit-source-id: c4b6112f6dd010d317060ac6640b34e4b725c695

Author: fkgozali