There's no reason not to enable DEP in 2019, especially given Go's
minimum operating system level.

RELNOTE=yes

Change-Id: I9c3bbc5b05a1654876a218123dd57b9c9077b780
Reviewed-on: https://go-review.googlesource.com/c/go/+/203601Reviewed-by: Alex Brainman <alex.brainman@gmail.com>