Rename the title of the node-exporter dashboard

[cbartz]

Issue

There is a dashboard title collision with the one in the grafana-agent machine charm.

Solution

Rename the title as suggested in https://github.com/canonical/observability/pull/206/files#r1863947198
uid collision will be addressed later as indicated in canonical/observability#206.

[sed-i]

Tested manually, works:

curl http://admin:[email protected]:3000/api/search   

[
  {
    "id": 1,
    "uid": "rYdddlPWk-1",
    "title": "System Resources (container)",
    "uri": "db/system-resources-container",
    "url": "/d/rYdddlPWk-1/system-resources-container",
    "slug": "",
    "type": "dash-db",
    "tags": [
      "linux"
    ],
    "isStarred": false,
    "sortMeta": 0
  }
]