Fix connectivity between prometheus and prometheus-node-exporter

Expected to have regressed after https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1008

This patch comes with its own downsides (as described in the comments
for matrix_prometheus_node_exporter_container_http_host_bind_port),
but at least there's:
- no security issue
- metrics remain readable from matrix-prometheus (even if the network metrics are inaccurate)

A better patch is certainly welcome.

roles/matrix-prometheus/tasks/setup_install.yml

@@ -19,24 +19,6 @@
     - "{{ matrix_prometheus_config_path }}"
     - "{{ matrix_prometheus_data_path }}"
 
-- block:
-    # Well, this actually creates the network if it doesn't exist, but..
-    # The network should have been created by `matrix-base` already.
-    # We don't rely on that other call and its result, because it runs
-    # on `--tags=setup-all`, but will get skipped during `--tags=setup-prometheus`.
-    - name: Fetch Matrix Docker network details
-      docker_network:
-        name: "{{ matrix_docker_network }}"
-        driver: bridge
-      register: matrix_docker_network_info
-
-    # The `matrix_docker_network_info.ansible_facts.docker_network` workaround is for Ansible < 2.8.
-    # See: https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/907
-    - set_fact:
-        matrix_prometheus_scraper_node_targets: ["{{ (matrix_docker_network_info.network|default(matrix_docker_network_info.ansible_facts.docker_network)).IPAM.Config[0].Gateway }}:9100"]
-  when: "matrix_prometheus_scraper_node_enabled|bool and matrix_prometheus_scraper_node_targets|length == 0"
-
-
 - name: Download synapse-v2.rules
   get_url:
     url: "{{ matrix_prometheus_scraper_synapse_rules_download_url }}"