[ios] Update signin disabled button from new mocks

https://drive.google.com/file/d/1qjgv_94Fbn_HqINFsR7XqEIUbhTAfNGG/view?usp=sharing

Bug: 1250375
Change-Id: Ie886073396bcd79ca413d209847875ede6103dfa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3172872


Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: David Jean <djean@chromium.org>
Cr-Commit-Position: refs/heads/main@{#923348}