[IOS][Omnibox] Dynamically adjust action button corner radius

Increased font size change the actions button shape.
This is fixed by changing the corner radius to be based on the button
height instead of a fixed value.

Fix screenshot: https://screenshot.googleplex.com/3SQ8mDd9UtBmPxa

Fixed: 350815850
Change-Id: Ie7a6945d78a389ca01b1f249d040a2066d91337f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5730300
Commit-Queue: Ameur Hosni <ameurhosni@google.com>
Auto-Submit: Ameur Hosni <ameurhosni@google.com>
Reviewed-by: Stepan Khapugin <stkhapugin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1331732}