Quarantine Http3RequestTests.POST_ClientCancellationUpload_RequestAbortRaised is flaky

## Failing Test(s)
- `Interop.FunctionalTests.Http3.Http3RequestTests.POST_ClientCancellationUpload_RequestAbortRaised`

## Details

This test has failed intermittently on `main` in the past 30 days:
- Build [1569737](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1569737&view=results) (2026-08-27)
- Build [1538879](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1538879&view=results) (2026-08-04)

The failures are separated by many passing runs in between (not back-to-back), so this is flakiness rather than a consistent regression. The test has never previously carried a `[QuarantinedTest]` attribute.

Quarantined via #aw_h3upload.

> Generated by [Daily Test Quarantine Management](https://github.com/dotnet/aspnetcore/actions/runs/33496438442) · auto · 240.4 AIC · ⌖ 10.9 AIC · ⊞ 4.3K · [◷](https://github.com/search?q=repo%3Adotnet%2Faspnetcore+is%3Aissue+%22gh-aw-workflow-call-id%3A+dotnet%2Faspnetcore%2Ftest-quarantine%22&type=issues)

Start with Interop.FunctionalTests.Http3.Http3RequestTests.POST_ClientCancellationUpload_RequestAbortRaised and compare the intermittent failures in builds 1569737 and 1538879. Reproduce or trace the cancellation behavior, then verify the test runs reliably on main and no longer needs quarantine.

Written by the indexing model from the issue text.