Add owner for enable-chromeos-account-manager flag

Context: https://sites.google.com/a/chromium.org/dev/flag-ownership

Bug: 820046
Change-Id: I8c64fd39cd8624f0810e1300ee3a4bc0caa0791b
Reviewed-on: https://chromium-review.googlesource.com/c/1343268Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Kush Sinha <sinhak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609684}

chrome/browser/flag-metadata.json

@@ -929,7 +929,7 @@
   },
   {
     "name": "enable-chromeos-account-manager",
-    // "owners": [ "your-team" ],
+    "owners": [ "sinhak@chromium.org" ],
     "expiry_milestone": 76
   },
   {