Update Challenge Selection's GetAuthenticationModeIcon()

For some challenge options,
CardUnmaskAuthenticationSelectionDialogView::GetAuthenticationModeIcon()
will never get called. This is due to the fact that this function only
gets called if there is one challenge option present. For OTP auth we
re-use the challenge selection dialog, but for CVC and 3DS auth the
auths have their own flows/dialogs.

Fixed: 362600079
Change-Id: I8e1a518a10b73a1d1f52b5b3cb729b35444eaa4d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5819373
Reviewed-by: Jan Keitel <jkeitel@google.com>
Reviewed-by: Siyu An <siyua@chromium.org>
Commit-Queue: Vinny Persky <vinnypersky@google.com>
Cr-Commit-Position: refs/heads/main@{#1348469}