Fix Bug 935719 - Tabzilla: Create an out of date version warning for users not on the current version

I think for Tabzilla, cherry picking code for the UITour API logic is probably the best way to go. I wouldn't like to have to load the whole UITour JS lib for every page on bedrock where Tabzilla is used, but I agree that shipping code that can't be properly tested until a future date is just not worth the potential risk. I think once this particular API call is in the release channel, then I would feel more easy about it - but I believe there is a chance some of the info returned in `data` could change between now and then.

I would be totally fine with removing the UITour logic in here for now, and then adding it back in once the code would actually be in a runnable/testable state. :+1: