Fix flaky TMPRL1104 duration-log assertions in test_extstore #5664

Job	Run time
cloud-test	2m 3s
build-lint-test (3.14, windows-latest)	20m 39s
build-lint-test (3.14, macos-arm)	13m 38s
build-lint-test (3.14, ubuntu-arm)	12m 21s
build-lint-test (3.10, windows-latest)	20m 44s
build-lint-test (3.14, ubuntu-latest)	22m 28s
check-protos	9m 41s
build-lint-test (3.10, ubuntu-arm)	12m 11s
features-tests / test	9m 15s
build-lint-test (3.10, macos-arm)	13m 47s
build-lint-test (3.10, ubuntu-latest)	16m 6s
test-latest-deps	11m 22s
	2h 44m 15s

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