[Fuchsia] Add ui/ozone/platform/scenic/OWNERS file.

Now all Fuchsia owners will be scenic ozone platform OWNERS.

Change-Id: I8377878a56785602b600bfdcd40e894c9a37415c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1744947Reviewed-by: Michael Spang <spang@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685380}

ui/ozone/platform/scenic/OWNERS

+file://build/fuchsia/OWNERS