[Uno-D] Sync promos in profile menu have "No thanks" button

Fixed: 342112623
Low-Coverage-Reason: TRIVIAL_CHANGE the changes in ios/chrome/browser/ui/authentication/signin_promo_view_mediator.mm are basically dead code and cannot be tested
Change-Id: I47a923bf563d18f6e6897eb96cc3ba9990434286
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5610452


Commit-Queue: David Roger <droger@chromium.org>
Reviewed-by: Ryan Sultanem <rsult@google.com>
Cr-Commit-Position: refs/heads/main@{#1312904}