test: unflake ReadAsyncTest #11092

Job	Run time
clirr	1m 13s
dependencies (17)	1m 24s
javadoc	2m 39s
lint	1m 33s
units (11)	3m 28s
units (8)	3m 37s
units (17)	3m 24s
units (21)	3m 17s
units-with-multiplexed-session (11)	3m 40s
units-with-multiplexed-session (8)	3m 26s
units-with-multiplexed-session (17)	3m 25s
windows	7m 54s
units-with-multiplexed-session (21)	3m 18s
	42m 18s

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