Fix timer periodic test flakiness #610

Job	Run time
rust_ci (macos-latest, beta)	1m 23s
rust_ci (ubuntu-latest, stable)	56s
rust_ci (macos-latest, stable)	1m 10s
rust_ci (windows-latest, stable)	1m 55s
rust_ci (windows-latest, beta)	2m 40s
rust_ci (ubuntu-latest, beta)	1m 24s
	9m 28s

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