Remove support for Debian Stretch

Debian Stretch's Long Term Support ended on 2022-06-30. Since the only
support still available (Extended LTS) is a commercial offering it does
not make sense to continue to support this platform if we are no longer
using it ourselves.

Author: mcdonnnj

meta/main.yml

@@ -20,7 +20,6 @@ galaxy_info:
         - any
     - name: Debian
       versions:
-        - stretch
         - buster
         - bullseye
         # Kali linux isn't an option here, but it is based on

molecule/default/Dockerfile_debian_9.j2

@@ -19,10 +19,6 @@ platforms:
   - image: amazonlinux:2
     name: amazonlinux2
     platform: amd64
-  - dockerfile: Dockerfile_debian_9.j2
-    image: debian:stretch-slim
-    name: debian9
-    platform: amd64
   - image: debian:buster-slim
     name: debian10
     platform: amd64

molecule/default/molecule-no-systemd.yml

@@ -24,15 +24,6 @@ platforms:
     privileged: yes
     volumes:
       - /sys/fs/cgroup:/sys/fs/cgroup:rw
-  - cgroupns_mode: host
-    command: /lib/systemd/systemd
-    image: geerlingguy/docker-debian9-ansible:latest
-    name: debian9-systemd
-    platform: amd64
-    pre_build_image: yes
-    privileged: yes
-    volumes:
-      - /sys/fs/cgroup:/sys/fs/cgroup:rw
   - cgroupns_mode: host
     command: /lib/systemd/systemd
     image: geerlingguy/docker-debian10-ansible:latest