The default scheduling on windows seems fairly erratic or is at least in the
VM that I'm running these tests on, so increase the timing slack a bit so the
test has a better chance of passing. It is still quite easy for it to fail
though, especially if you for instance manipulate the terminal window somehow
while running the tests but it does not really matter in any case as this test
serves its purpose in testing the PBD::MMTimers API.
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