[Android] Update OWNERS information (childaccounts)

https://docs.google.com/document/d/11syJ3z5uLOE07ctP_17Mqfuzq_-Gb7PvoVvsjUdIDFQ

Bug: 1112872
Change-Id: Iba9af88e2c7ca28321ae32b8a60735097943e874
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2360696
Auto-Submit: Fred Mello <fredmello@chromium.org>
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Commit-Queue: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#799093}

chrome/android/java/src/org/chromium/chrome/browser/childaccounts/OWNERS

+bsazonov@chromium.org
+msarda@chromium.org
+
+# COMPONENT: Services>Signin
+# TEAM: chrome-signin-team@google.com
+# OS: Android
\ No newline at end of file