Clarify documentation

Hello, could you please clarify this documentation to explain what is meant by:
> The SemaphoreSlim class represents a lightweight, fast semaphore that can be used for waiting within a single process when **wait times are expected to be very short**.

Searching for my answer on StackOverflow - I still think it is not clear that:
A) It is possible to use it on long waits - eg. more than 5 minutes
B) It means that it is more performant when short wait times are expected

Thanks

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#### Document Details

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* ID: 51e078fd-3a63-8b58-49f8-67e49df9bc9f
* Version Independent ID: f082f7b2-e1a3-aa31-1081-5ca11c954d80
* Content: [Semaphore and SemaphoreSlim](https://docs.microsoft.com/en-us/dotnet/standard/threading/semaphore-and-semaphoreslim)
* Content Source: [docs/standard/threading/semaphore-and-semaphoreslim.md](https://github.com/dotnet/docs/blob/main/docs/standard/threading/semaphore-and-semaphoreslim.md)
* Product: **dotnet-fundamentals**
* GitHub Login: @BillWagner
* Microsoft Alias: **wiwagn**