Fix SendRequestAsync hang on Streamable HTTP SSE retry #2360

Job	Run time
build (windows-latest, Release)	9m 6s
build (macos-latest, Release)	7m 0s
build (ubuntu-latest, Debug)	12m 44s
build (macos-latest, Debug)	6h 5m 1s
build (windows-latest, Debug)	9m 46s
build (ubuntu-latest, Release)	11m 39s
publish-coverage	-1s
	6h 55m 15s

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