[iOS] Remove items from section instead of removing the section itself

Before this CL, on the selection of the country, the removal of whole
section and recreating it, resulted in the distorted view. Therefore,
with this CL, the items in the section are removed and readded.

Bug: 1482269
Change-Id: Iebdcce09b28201be9c3c0f1333dc959fc977bbdb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5498916
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Vidhan Jain <vidhanj@google.com>
Cr-Commit-Position: refs/heads/main@{#1294384}