Add new Guest OS OWNERS: sidereal@, hollingum@, juwa@

Change-Id: Ie57165228901ff1c85907ea7c1e20829b3a04e70
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1884403Reviewed-by: Joel Hockey <joelhockey@chromium.org>
Commit-Queue: Timothy Loh <timloh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710583}

chrome/browser/chromeos/crostini/OWNERS

-benwells@chromium.org
-joelhockey@chromium.org
-nverne@chromium.org
-timloh@chromium.org
+file://chrome/browser/chromeos/guest_os/OWNERS
 
 per-file *.mojom=set noparent
 per-file *.mojom=file://ipc/SECURITY_OWNERS

chrome/browser/chromeos/guest_os/OWNERS

-benwells@chromium.org
+hollingum@google.com
 joelhockey@chromium.org
+juwa@google.com
 nverne@chromium.org
+sidereal@google.com
 timloh@chromium.org
 
 # COMPONENT: UI>Shell>Containers