title: Firebase Phone Authentication pops up a reCAPTCHA verification window on iOS even if Background Modes and Push Notifications are enabled
body: <p>I implemented Phone Authentication with Firebase on iOS. Authentication works. However, on iOS, a reCAPTCHA window pops up. I tried to enable Silent Notifications by enabling Background Modes and Push Notifications. It is skipping the reCAPTCHA test but it still pops up a blank page with a loading bar to do the verification automatically. Is there an extra step that I'm missing? Also, I'm new to XCode so I might be missing a configuration step (for example I didn't click any checkboxes on the Background Modes dropdown).</p>
  
  <p>Do you have any suggestions on what I could be missing?</p>