Add sinansahin to metrics android subdirectory OWNERS

Change-Id: I95e0499c09e8eef37773c5d10f505ba8674eed4b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4032047


Reviewed-by: Wenyu Fu <wenyufu@chromium.org>
Commit-Queue: Sinan Sahin <sinansahin@google.com>
Cr-Commit-Position: refs/heads/main@{#1072311}