Flaky test: DataBeforeHeaders_UnexpectedFrameError

[JunTaoLuo]

Build: https://dev.azure.com/dnceng/public/_build/results?buildId=1070757&view=results

Logs:

Assert.Equal() Failure
Expected: UnexpectedFrame
Actual:   0
   at Microsoft.AspNetCore.Server.Kestrel.Core.Tests.Http3TestBase.Http3RequestStream.WaitForStreamErrorAsync(Http3ErrorCode protocolError, String expectedErrorMessage) in /_/src/Servers/Kestrel/test/InMemory.FunctionalTests/Http3/Http3TestBase.cs:line 458
   at Microsoft.AspNetCore.Server.Kestrel.Core.Tests.Http3StreamTests.DataBeforeHeaders_UnexpectedFrameError() in /_/src/Servers/Kestrel/test/InMemory.FunctionalTests/Http3/Http3StreamTests.cs:line 1632
--- End of stack trace from previous location ---

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We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. Because it's not immediately obvious that this is a bug in our framework, we would like to keep this around to collect more feedback, which can later help us determine the impact of it. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
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