Do not delete Prometheus/Grafana Docker images

Same reasoning as in 1cd251ed78

roles/matrix-grafana/tasks/setup.yml

@@ -108,8 +108,3 @@
     daemon_reload: yes
   when: "not matrix_grafana_enabled|bool and matrix_grafana_service_stat.stat.exists"
 
-- name: Ensure matrix-grafana Docker image doesn't exist
-  docker_image:
-    name: "{{ matrix_grafana_docker_image }}"
-    state: absent
-  when: "not matrix_grafana_enabled|bool"

roles/matrix-prometheus-node-exporter/tasks/setup.yml

@@ -52,9 +52,3 @@
   service:
     daemon_reload: yes
   when: "not matrix_prometheus_node_exporter_enabled|bool and matrix_prometheus_node_exporter_service_stat.stat.exists"
-
-- name: Ensure matrix-prometheus-node-exporter Docker image doesn't exist
-  docker_image:
-    name: "{{ matrix_prometheus_node_exporter_docker_image }}"
-    state: absent
-  when: "not matrix_prometheus_node_exporter_enabled|bool"

roles/matrix-prometheus/tasks/setup_uninstall.yml

@@ -23,9 +23,3 @@
   service:
     daemon_reload: yes
   when: "matrix_prometheus_service_stat.stat.exists|bool"
-
-- name: Ensure matrix-prometheus Docker image doesn't exist
-  docker_image:
-    name: "{{ matrix_prometheus_docker_image }}"
-    state: absent
-  when: "not matrix_prometheus_enabled|bool"