[iOS] Remove BUILD.gn target name when it is the same as folder name

It is a cleanup of the code base and provide better example for the
future.

This CL was uploaded by an experimental version of git cl split
(https://crbug.com/389069356).

R=rohitrao@chromium.org

Bug: None
Change-Id: I076a594e9d5d4e6ff8ef06f41da61eeae8cdf5fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6547257
Auto-Submit: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1463435}