Adding Katie to the chrome/browser/accessibility OWNERS file

NOTRY=true

Bug: none
Change-Id: I49f929bb9806d49a356c686fa913acce4a55c47a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1509456
Auto-Submit: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638771}

chrome/browser/accessibility/OWNERS

 file://ui/accessibility/OWNERS
 
+katie@chromium.org
+
 # TEAM: chromium-accessibility@chromium.org
 # COMPONENT: UI>Accessibility