[UNOp2][Android] Make sign-in promo tests pass with UNO flag

This CL makes some sign-in promo related test run with UNO flag enabled
by default, and fixes failures accordingly.

Fixed: 345115197
Change-Id: Iff203418d97b53af3067e2c9a6b1a27f61007a2b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5604593


Auto-Submit: Menghan Yang <myuu@google.com>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Commit-Queue: Menghan Yang <myuu@google.com>
Cr-Commit-Position: refs/heads/main@{#1312821}