Backup Codes unintentionally regenerated when switching devices, clearing local storage, etc

[iandunn]

1. Setup Backup Codes
2. Delete the WPORG_2FA_HAS_BACKUP_CODES_BEEN_SAVED local storage item
3. Refresh

Your original Backup Codes from step 1 will be regenerated. Step 2 artificially creates the situation, but the same thing should happen when viewing the screen from your phone when it was originally setup on your laptop, switching to a different browser, clearing your browser data, etc.

That was mentioned in #221, but I'm not sure the implications were obvious. When this happens it means that the codes that folks originally saved (maybe months or years prior) will be overwritten, and they'll have to save the new ones, or they risk being locked out of their account. At best that's annoying/inconvenient, but I worry that it'll create situations where folks didn't write down the new keys and lose their account.