[iOS] actionSheetCoordinator stopped

According to ChromeCoordinator invariant, all coordinators should be
stopped before being deallocated. This CL ensures that whatever the user chose, the coordinator is stopped; whether they tap a button or
dismiss by tapping outside (which call the cancel button)

In ActionSheetCoordinator, a cancel item is always added.
So adding this cancel element is not adding a new item, it’s only
ensuring it stops the coordinator

Bug: 1466233
Change-Id: I3c2e975e3643b9fa25bbe49ef409eb75abb7e2f3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4701287
Commit-Queue: Arthur Milchior <arthurmilchior@chromium.org>
Reviewed-by: Tanmoy Mollik <triploblastic@google.com>
Cr-Commit-Position: refs/heads/main@{#1179948}