[CrOS SMB] Add amistry@ as owner for WebUI dialog.

This CL also removes myself as an OWNER, though I am still an OWNER of
the parent directory.

Change-Id: I0ec994ab5be2afca356ff0120f45f64a8a489067
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2013521
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Anand Mistry <amistry@chromium.org>
Auto-Submit: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Anand Mistry <amistry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#733805}

chrome/browser/resources/chromeos/smb_shares/OWNERS

-khorimoto@chromium.org
\ No newline at end of file
+amistry@chromium.org
+
+# COMPONENT: Enterprise>ActiveDirectory
\ No newline at end of file