The current install flow for PWAs (when beforeinstallprompt.preventDefault()) has been called is:

1. user clicks on some UI in the web page, triggering a call to beforeinstallprompt.prompt().
2. we show the app install banner, which the user must click to accept
3. we show the app install dialog, which contains no editable fields, and the user must click to accept.

We don't need two confirmation mechanisms (#2 & #3), and the install banner is also redundant with respect the the UI element in #1.  So we should remove #2 (the app install banner).

We will still show the banner when the beforeinstallprompt.preventDefault() is not called.