Bump test_ucx::test_stress timeout

[TomAugspurger]

This bumps the timeout on distributed/comm/tests/test_ucx.py::test_stress from 60s to 120s. On the machine I have access to it takes about 70s to run.

I haven't looked into whether something has happened to slow this test down (cc @pentschev if you have thoughts on whether this is worth me looking into more).

[pentschev]

It's hard to say if anything happened that directly impacted this test or something else has happened, it could be just the machine you're running on takes more time for some reason and the timeout was tight and not being tested lately since CI was disabled. Similarly, we have issues with timeouts that are fine for years and suddenly they become a problem in Dask-CUDA. Until this day I haven't found a good explanation for any of that.

[github-actions]

Unit Test Results

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

    27 files  ±0      27 suites  ±0   11h 40m 43s ⏱️ - 15m 43s
 4 116 tests ±0   4 001 ✅ +2    111 💤 ±0  4 ❌  - 1 
51 615 runs   - 1  49 314 ✅ +1  2 297 💤 ±0  4 ❌  - 1 

For more details on these failures, see this check.

Results for commit c57be5c. ± Comparison against base commit 5589049.