PyPy3.11 test fixes

[mgorny]

Fix a regex in a single test, and add pypy311 to tox.ini targets using pytrace only.

[nedbat]

Thanks. On my Mac, I also see an error for test SigtermTest.test_sigterm_still_runs:

>       assert out == "START\nSIGTERM\nEND\n"
E       assert 'START\nSIGTERM\nProcess Process-1:\nTraceback (most recent call last):\n  File "/usr/local/pyenv/pyenv/versions/pypy3.11-7.3.18/lib/pypy3.11/multiprocessing/process.py", line 314, in _bootstrap\n    self.run()\n  File "/usr/local/pyenv/pyenv/versions/pypy3.11-7.3.18/lib/pypy3.11/multiprocessing/process.py", line 108, in run\n    self._target(*self._args, **self._kwargs)\n  File "/private/var/folders/6j/khn0mcrj35d1k3yylpl8zl080000gn/T/pytest-of-ned/pytest-37/t2/handler.py", line 12, in subproc\n    time.sleep(.1)\nOSError: [Errno -1] Unknown error: -1\n' == 'START\nSIGTERM\nEND\n'
E
E           START
E           SIGTERM
E         - END
E         + Process Process-1:
E         + Traceback (most recent call last):
E         +   File "/usr/local/pyenv/pyenv/versions/pypy3.11-7.3.18/lib/pypy3.11/multiprocessing/process.py", line 314, in _bootstrap
E         +     self.run()
E         +   File "/usr/local/pyenv/pyenv/versions/pypy3.11-7.3.18/lib/pypy3.11/multiprocessing/process.py", line 108, in run
E         +     self._target(*self._args, **self._kwargs)
E         +   File "/private/var/folders/6j/khn0mcrj35d1k3yylpl8zl080000gn/T/pytest-of-ned/pytest-37/t2/handler.py", line 12, in subproc
E         +     time.sleep(.1)
E         + OSError: [Errno -1] Unknown error: -1

/Users/ned/coverage/trunk/tests/test_concurrency.py:809: AssertionError

[nedbat]

Here's a failure on GitHub Actions: https://github.com/nedbat/coveragepy/actions/runs/13390614273