Adds some accessibility team owners on a11y flags.

Set the --enable-experimental-accessibility-features flag to
never expire. This flag is used by multiple a11y features and
will continue to be used for the forseable future.

Change-Id: I18cf355e1116a69c87c45928e250295eeb2787b3
Reviewed-on: https://chromium-review.googlesource.com/c/1340783
Commit-Queue: Katie Dektar <katie@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609834}

chrome/browser/flag-metadata.json

@@ -698,7 +698,7 @@
   },
   {
     "name": "enable-accessibility-object-model",
-    // "owners": [ "your-team" ],
+    "owners": [ "//ui/accessibility/OWNERS" ],
     "expiry_milestone": 76
   },
   {
@@ -1123,7 +1123,7 @@
   },
   {
     "name": "enable-experimental-accessibility-features",
-    // "owners": [ "your-team" ],
+    "owners": [ "//ui/accessibility/OWNERS" ],
     "expiry_milestone": 76
   },
   {