Fix SendRequestAsync hang on Streamable HTTP SSE retry #2367

Job	Run time
build (windows-latest, Release)	12m 18s
build (macos-latest, Debug)	4m 54s
build (ubuntu-latest, Debug)	6m 32s
build (macos-latest, Release)	7m 0s
build (windows-latest, Debug)	11m 14s
build (ubuntu-latest, Release)	6m 53s
publish-coverage / publish-coverage	57s
	49m 48s

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