Determine next steps on birthday data

Summary

Aside from UX issues with the selector, currently the birthday data (and city data) isn't even in a usable form processing-wise.

These are our options:

1. Remove it entirely
2. Update selector, deal with legacy data and make it usable (Preferred)

There are various issues with the UI as well (eg there is no way to easily change birthyear under edit channel>date of birth on mobile app. User has to scroll through each year month-by-month.)