In 10c1f1dc80 I fixed
`make_group0_history_state_id_mutation` to use correct timestamp
resolution (microseconds instead of milliseconds) which was supposed to
fix the flakiness of `test_group0_history_clearing_old_entries`.
Unfortunately, the test is still flaky, although now it's failing at a
later step -- this is because I was sloppy and I didn't adjust this
second part of the test to also use microsecond resolution. The test is
counting the number of entries in the `system.group0_history` table that
are older than a certain timestamp, but it's doing the counting using
millisecond resolution, causing it to give results that are off by one
sometimes.
Fix it by using microseconds everywhere.
Fixes#14653Closes#14670
(cherry picked from commit 9d4b3c6036)
6273c4df35