test: unflake ReadAsyncTest #11095

Job	Run time
javadoc	2m 46s
lint	1m 46s
units (11)	3m 27s
dependencies (17)	1m 20s
units (17)	3m 17s
units (8)	3m 40s
units (21)	3m 16s
units-with-multiplexed-session (11)	3m 28s
units-with-multiplexed-session (17)	3m 30s
units-with-multiplexed-session (8)	3m 29s
windows	8m 14s
units-with-multiplexed-session (21)	3m 48s
clirr	1m 16s
	43m 17s

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