update_chroot: delete --useoldpkg-atoms=dev-lang/go

So that the change (CL:615754) to the toolchain package dev-lang/go will
be picked up.

BUG=b:64542183
TEST=trybot

Change-Id: I9c0db8a6f9c8a3c69694afe4b5122044e8c6cf5c
Reviewed-on: https://chromium-review.googlesource.com/634220
Trybot-Ready: Ke Wu <mikewu@google.com>
Reviewed-by: Rahul Chaudhry <rahulchaudhry@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Ke Wu <mikewu@google.com>
Tested-by: Ke Wu <mikewu@google.com>
diff --git a/update_chroot b/update_chroot
index 7bf4570..fceeb2e 100755
--- a/update_chroot
+++ b/update_chroot
@@ -97,7 +97,6 @@
   # process only takes place when the chromiumos sdk builder finishes
   # a successful build.
   EMERGE_FLAGS+=(
-    --useoldpkg-atoms=dev-lang/go
     --useoldpkg-atoms=sys-devel/binutils
     --useoldpkg-atoms=sys-devel/clang
     --useoldpkg-atoms=sys-devel/gcc