update_payload: Remove instances to au-generator

We now do paygen in chroot. There is no need for au-generator anymore. So remove
all references to it.

BUG=chromium:808495
TEST=tryjob payload

Change-Id: I0d0e76cc1dd7a742abdd9b3b457709044af98862
Reviewed-on: https://chromium-review.googlesource.com/1085547
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Nicolas Norvez <norvez@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>
diff --git a/scripts/brillo_update_payload b/scripts/brillo_update_payload
index dd6f80d..9dae42b 100755
--- a/scripts/brillo_update_payload
+++ b/scripts/brillo_update_payload
@@ -82,7 +82,7 @@
 }
 
 # Loads shflags. We first look at the default install location; then look for
-# crosutils (chroot); finally check our own directory (au-generator zipfile).
+# crosutils (chroot); finally check our own directory.
 load_shflags() {
   local my_dir="$(dirname "$(readlink -f "$0")")"
   local path