TrimmerRootDescriptor does not work on .net core 3.1, that option is completely ignored.

It should be mentioned in documentation, otherwise developer is wondering why it does not work.

Document Details

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• ID: 811fc2ce-1f05-5be2-d033-7fce35e49525
• Version Independent ID: fca1c728-4716-8c28-89e1-02eb947bf602
• Content: Trimming options - .NET
• Content Source: docs/core/deploying/trimming-options.md
• Product: dotnet-fundamentals
• GitHub Login: @sbomer
• Microsoft Alias: svbomer