Perfcollect doesn't need crossgen since .net6?

After looking at https://github.com/microsoft/perfview/issues/1550, it seems that perfcollect doesn't depend on crossgen anymore starting with .NET6. Moreover, crossgen itself is renamed to crossgen2, which is not even looked for by perfcollect script.
Based on my personal experience, I believe other people may spend considerable amount of time figuring these details out, so I suggest that https://learn.microsoft.com/en-us/dotnet/core/diagnostics/trace-perfcollect-lttng is updated to reflect this.

Thanks!

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* ID: 7dd230f8-907f-5f07-e3ab-7ad37fee3aa4
* Version Independent ID: ac6cc555-a033-766d-0597-bd9bda98820f
* Content: [Tracing .NET applications with PerfCollect. - .NET](https://learn.microsoft.com/en-us/dotnet/core/diagnostics/trace-perfcollect-lttng)
* Content Source: [docs/core/diagnostics/trace-perfcollect-lttng.md](https://github.com/dotnet/docs/blob/main/docs/core/diagnostics/trace-perfcollect-lttng.md)
* Service: **dotnet-fundamentals**
* GitHub Login: @tommcdon
* Microsoft Alias: **tommcdon**