libbrillo: remove unused header

This header is gone in future libchromes and we removed all of
the references to dbus::FileDescriptor in previous CLs.

BUG=b:37434548
TEST=emerge

Change-Id: I0034a1fea6c07ce2a3f95702f363d528662e8225
Reviewed-on: https://chromium-review.googlesource.com/1003595
Commit-Ready: Eric Caruso <ejcaruso@chromium.org>
Tested-by: Eric Caruso <ejcaruso@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
1 file changed