Drop chronos from group lpadmin

We've decided to run printer add/remove over dbus using debugd.
Thus, chronos will no longer need to run as lpadmin.  chronos is
in lp so it can still print and cancel jobs that it started.

BUG=chromium:633382
TEST=`test_that ... security_AccountsBaseline`
CQ-DEPEND=Iadd0c23ea1949d05c4a2f999883fbe81a4170eb1

Change-Id: I68824c77da1203843d21212f5487df82997b210a
Reviewed-on: https://chromium-review.googlesource.com/370678
Commit-Ready: Sean Kau <skau@chromium.org>
Tested-by: Sean Kau <skau@chromium.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
diff --git a/profiles/base/accounts/group/lpadmin b/profiles/base/accounts/group/lpadmin
index d663276..c32e72c 100644
--- a/profiles/base/accounts/group/lpadmin
+++ b/profiles/base/accounts/group/lpadmin
@@ -1,3 +1,3 @@
 group:lpadmin
 gid:269
-users:chronos,cups,lpadmin
+users:cups,lpadmin