Fix flaky test_task_counter

[crusaderky]

https://github.com/dask/distributed/actions/runs/5966044981/job/16184860068?pr=8127

On Windows CI:

>       assert_time(elapsed["x", "flight"], 0.2)

    def assert_time(actual, expect):
        # timer accuracy in Windows can be very poor;
        # see awful hack in distributed.metrics
        margin_lo = 0.099 if WINDOWS else 0
        # sleep() has been observed to have up to 450ms lag on MacOSX GitHub CI
        margin_hi = 0.6 if MACOS else 0.1
>       assert expect - margin_lo <= actual < expect + margin_hi
E       assert 0.355125300000509 < (0.2 + 0.1)

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

       21 files  +       1         21 suites  +1   11h 57m 42s ⏱️ + 26m 25s
  3 779 tests ±       0    3 671 ✔️ +       5     107 💤 ±  0  1 ❌  - 5 
36 531 runs  +1 385  34 729 ✔️ +1 357  1 801 💤 +35  1 ❌  - 7 

For more details on these failures, see this check.

Results for commit 0acd0f5. ± Comparison against base commit 22eb33a.