node_exporter: Drop os specific var files

roles/node_exporter/handlers/main.yml

@@ -1,5 +1,10 @@
 ---
 - name: Restart node_exporter
   ansible.builtin.service:
-    name: "{{ node_exporter_service }}"
+    name: >-
+      {% if ansible_distribution == "OpenBSD" -%}
+      {{ "node_exporter" -}}
+      {% else -%}
+      {{ "prometheus-node-exporter" -}}
+      {% endif -%}
     state: restarted