It is useful to exclude the change author when suggesting owners.

Change-Id: I3321c013271f6cea1098abba59b509800818917e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2669680
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Auto-Submit: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Josip Sokcevic <sokcevic@google.com>