Remove dead permissions code for MetricsDashboard::Annotations

What does this MR do and why?

Changes: Removes the read/admin permissions for metrics_dashboard_annotations, as those features have been removed.

Context: This MR cleans up a portion of dead code related to the removal of devopsmonitor Category:Metrics features. The Metrics Dashboard & Prometheus Metrics/Alerts (used for monitoring apps deploying using gitlab) were deprecated in 14.7 and removed from the product in 16.0.

• grouprespond related issue: Metrics: Delete models & database tables/columns (#397142)
• Monitor:Metrics removal epic: Monitor: Metrics Deprecation and Removal (&10107)
• Reference MR with all related removals: Draft: Remove all remaining metrics dashboard-r... (!160325 - closed)
• Metrics removal is blocking cells: Drop old unused tables for prometheus alerts (#461838 - closed)

Dummy mutation

mutation CreateAnnotation {
  createAnnotation(input: {
    startingAt: "2024-02-15T22:37:40.958Z",
    dashboardPath: "apple/pie",
    description: "pumpkinn pie"
  }) {
    errors
  }
}

API Response before

{
  "errors": [
    {
      "message": "The resource that you are attempting to access does not exist or you don't have permission to perform this action",
      "locations": [
        {
          "line": 15,
          "column": 3
        }
      ],
      "path": [
        "createAnnotation"
      ]
    }
  ],
  "data": {
    "createAnnotation": null
  }
}

API response after

{
  "errors": [
    {
      "message": "The resource that you are attempting to access does not exist or you don't have permission to perform this action",
      "locations": [
        {
          "line": 2,
          "column": 3
        }
      ],
      "path": [
        "createAnnotation"
      ]
    }
  ],
  "data": {
    "createAnnotation": null
  }
}

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