Fix root cause of flaky test crash [gw0] node down: Not properly terminated

[Pijukatel]

Seems like this happens only on Windows and Python3.12, always the last test crahes with
[gw0] node down: Not properly terminated

Seems like it was introduced when bumping uvicorn
#1421

[vdusek]

I'm reopening this because #1447 did not fix the root cause. We should make our setup work even with uvicorn > 0.35.