Flaky test: Http2_MultipleConnectionsEnabled_ConnectionLimitNotReached_ConcurrentRequestsSuccessfullyHandled

[GrabYourPitchforks]

Test Http2_MultipleConnectionsEnabled_ConnectionLimitNotReached_ConcurrentRequestsSuccessfullyHandled appears to be flaky. Occasionally timing out and causing CI failures.

See:
https://github.com/dotnet/runtime/pull/36252/checks?check_run_id=951684309
https://github.com/dotnet/runtime/pull/40426/checks?check_run_id=951565333

    System.Net.Http.Functional.Tests.SocketsHttpHandlerTest_Http2.Http2_MultipleConnectionsEnabled_ConnectionLimitNotReached_ConcurrentRequestsSuccessfullyHandled [FAIL]
      System.TimeoutException : Task timed out after 00:01:00
      Stack Trace:
        /_/src/libraries/Common/tests/System/Threading/Tasks/TaskTimeoutExtensions.cs(41,0): at System.Threading.Tasks.TaskTimeoutExtensions.TimeoutAfter(Task task, TimeSpan timeout)
        /_/src/libraries/System.Net.Http/tests/FunctionalTests/SocketsHttpHandlerTest.cs(2213,0): at System.Net.Http.Functional.Tests.SocketsHttpHandlerTest_Http2.PrepareConnection(Http2LoopbackServer server, HttpClient client, UInt32 maxConcurrentStreams, Int32 readTimeout, Int32 expectedWarpUpTasks)
        /_/src/libraries/System.Net.Http/tests/FunctionalTests/SocketsHttpHandlerTest.cs(2008,0): at System.Net.Http.Functional.Tests.SocketsHttpHandlerTest_Http2.Http2_MultipleConnectionsEnabled_ConnectionLimitNotReached_ConcurrentRequestsSuccessfullyHandled()
        --- End of stack trace from previous location ---
  Finished:    System.Net.Http.Functional.Tests
=== TEST EXECUTION SUMMARY ===
   System.Net.Http.Functional.Tests  Total: 2085, Errors: 0, Failed: 1, Skipped: 14, Time: 131.149s

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[MihaZupan]

Looks like the test is failing even after #40464