test: fix flaky test on slow machines

[kxxt]

Send the interrupt a little later so that we won't end up interrupting it too early, which will cause the output mismatch.

I got the following result from a riscv64 board and emulator:

!!!!!!!!!!!!!!!!!!!!!!!!!!!!! KeyboardInterrupt !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
/usr/lib/python3.11/unittest/__init__.py:93: KeyboardInterrupt
(to show a full traceback on KeyboardInterrupt use --full-trace)

============================= test session starts ==============================
platform linux -- Python 3.11.3, pytest-7.3.1, pluggy-1.0.0
rootdir: /build/python-alt-pytest-asyncio/src/alt-pytest-asyncio-release-0.7.0/tests/interrupt_test
configfile: pytest.ini
plugins: alt-pytest-asyncio-0.7.0, noseOfYeti-2.4.1
collected 5 items

tests/test_example.py .F

=================================== FAILURES ===================================
__________________________ test_bb_shows_failed_tests __________________________
tests/test_example.py:20: in test_bb_shows_failed_tests
    assert False, "NOOOOO"
E   AssertionError: NOOOOO
E   assert False
=========================== short test summary info ============================
FAILED tests/test_example.py::test_bb_shows_failed_tests - AssertionError: NO...
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! KeyboardInterrupt !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
/usr/lib/python3.11/selectors.py:468: KeyboardInterrupt
(to show a full traceback on KeyboardInterrupt use --full-trace)
========================= 1 failed, 1 passed in 1.78s ==========================

[delfick]

ah yeah. sure. Thanks!