`test_multi_progressbar_widget_after_close` failed on CI

In [this CI run]( https://github.com/dask/distributed/runs/6416006913?check_suite_focus=true ), `test_multi_progressbar_widget_after_close` timed out.

```python
> raise asyncio.TimeoutError(
f"Test timeout after {timeout}s.\n"
"========== Test stack trace starts here ==========\n"
f"{buffer.getvalue()}"
) from None
E asyncio.exceptions.TimeoutError: Test timeout after 30s.
E ========== Test stack trace starts here ==========
E Stack for wait_for=()]>> (most recent call last):
E File "D:\a\distributed\distributed\distributed\diagnostics\tests\test_widgets.py", line 172, in test_multi_progressbar_widget_after_close
E await p.listen()

distributed\utils_test.py:1078: TimeoutError
---------------------------- Captured stdout call -----------------------------
Dumped cluster state to test_cluster_dump\test_multi_progressbar_widget_after_close.yaml
---------------------------- Captured stderr call -----------------------------
2022-05-13 01:26:05,047 - distributed.worker - WARNING - Compute Failed
Key: e
Function: throws
args: (2)
kwargs: {}
Exception: "RuntimeError('hello!')"

----- generated xml file: D:\a\distributed\distributed\reports\pytest.xml -----
```