Remove superfluous legacy DBus includes

This header pulls in glib dependencies which aren't used in these
codebases.

BUG=chromium:508218
TEST=trybots

Change-Id: Iecf8dfcdd8064b1feb694382eea55c3f0df572d3
Reviewed-on: https://chromium-review.googlesource.com/284053


Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
Trybot-Ready: Christopher Wiley <wiley@chromium.org>