WORKSPACE: Update to latest Debian for security fixes
WORKSPACE: Update to latest Debian for security fixes

The GCP security scanner is warning about issues with python2.7 and
ncurses. Fixes were released on 2019-10-11 and 2019-11-02, after the
last update. Debian 9 (stretch) does not seem to have fixes for these
issues.

ncurses: https://security-tracker.debian.org/tracker/CVE-2019-17595
python2.7: https://security-tracker.debian.org/tracker/CVE-2019-16056

The version updates for all packages in Debian 10 were:

base-files 10.3+deb10u1 -> 10.3+deb10u2
libfreetype6 2.9.1-3 -> 2.9.1-3+deb10u1
libncursesw6 6.1+20181013-2+deb10u1 -> 6.1+20181013-2+deb10u2
libpython2.7-minimal 2.7.16-2 -> 2.7.16-2+deb10u1
libpython2.7-stdlib 2.7.16-2 -> 2.7.16-2+deb10u1
libtinfo6 6.1+20181013-2+deb10u1 -> 6.1+20181013-2+deb10u2
python2.7-minimal 2.7.16-2 -> 2.7.16-2+deb10u1
tzdata 2019b-0+deb10u1 -> 2019c-0+deb10u1

istio/distroless,istio/distroless,GoogleContainerTools/distroless,GoogleContainerTools/distroless,GoogleContainerTools/distroless,istio/distroless