[Fuchsia] Add OWNERS rule to //ui for all Fuchsia-specific files.

Remove a couple of directory-level OWNERS files in favour of top-level
//ui/OWNERS rules for all *fuchsia* and *scenic* files &* directories.

Change-Id: Ie2b20f5c272cff9e75859b62a03fc4a13c889a19
Reviewed-on: https://chromium-review.googlesource.com/c/1450702
Commit-Queue: Wez <[email protected]>
Reviewed-by: Nico Weber <[email protected]>
Auto-Submit: Wez <[email protected]>
Cr-Commit-Position: refs/heads/master@{#628522}

Author: Wez

ui/OWNERS

@@ -11,3 +11,7 @@ per-file BUILD.gn=*
 
 # Translation artifacts:
 per-file *.xtb=file://tools/translation/TRANSLATION_OWNERS
+
+# For Fuchsia-specific changes:
+per-file *fuchsia*=file://build/fuchsia/OWNERS
+per-file *scenic*=file://build/fuchsia/OWNERS