Update the websocket client disconnect section with keep alive timeout

[BrennanConroy]

Description

We added docs in #33460 but they only made it to release notes.

We should update the main docs with this information.
https://learn.microsoft.com/en-us/aspnet/core/fundamentals/websockets?view=aspnetcore-9.0#handle-client-disconnects

Page URL

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/websockets?view=aspnetcore-9.0#handle-client-disconnects

Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/fundamentals/websockets.md

Document ID

762efeed-010e-f422-03d0-22d6681b2851

Article author

@wadepickett

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Associated WorkItem - 343313