gh-116112: Fix ResourceWarning in test_asyncio.test_stream

[sobolevn]

I've done local testing:

» ./python.exe -We -m test test_asyncio.test_streams -m test_unhandled_cancel
Using random seed: 3038344157
0:00:00 load avg: 0.73 Run 1 test sequentially
0:00:00 load avg: 0.73 [1/1] test_asyncio.test_streams

== Tests result: SUCCESS ==

1 test OK.

Total duration: 194 ms
Total tests: run=1 (filtered)
Total test files: run=1/1 (filtered)
Result: SUCCESS

It works. This solution was proposed by @CendioOssman in #116112 (comment)

Co-authored-by: @CendioOssman

• Issue: test_asyncio.test_streams raises a ResourceWarning #116112

[gvanrossum]

Thanks, I did some local testing too and it seems to work.

[sobolevn]

Thank you! 👍

I've merged this, no backports, because #115661 did not have any.