Update the list for .NET 6

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• ID: f6487cae-3320-584d-6c27-fc712ec03e72
• Version Independent ID: 846981e7-bc47-0df8-8621-22282de18ef3
• Content: Unsupported APIs on .NET Core and .NET 5+
• Content Source: docs/core/compatibility/unsupported-apis.md
• Product: dotnet-fundamentals
• GitHub Login: @gewarren
• Microsoft Alias: gewarren