Remove recommendations opt out which is no longer funtional

[wadepickett]

Remove the following line: from aspnetcore/docfx.json:

  "recommendations": {
    "**/tutorials/**/**.md": "false"
  }

Why:
This is no longer an opt out option to prevent the "Additonal resources" section from being created, since 2023, so this setting does nothing now.

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Associated WorkItem - 549113