Staging strings not updated

[gideonthomas]

For some reason, the strings in dist/nls are not updated when we add new strings to the locales folder. Cannot reproduce this locally. The properties2js script should take care of generating the dist/nls files which seems to happen if you look at the travis build and these files seem to be uploaded to S3 as well but when you access them using https://mozillathimblelivepreview.net/bramble/staging/dist/nls/root/strings.js, it shows the old strings.