gh-96710: Make the test timing more lenient for the int/str DoS regression test....

gh-96710: Make the test timing more lenient for the int/str DoS regression test. (#96717)

A regression would still absolutely fail and even a flaky pass isn't
harmful as it'd fail most of the time across our N system test runs.

Windows has a low resolution timer and CI systems are prone to odd
timing so this just gives more leeway to avoid flakiness.