test_faulthandler: fix regex on the check_dump_traceback_threads() traceback
The traceback may contain "_is_owned":
Thread 0x40962b90:
File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/threading.py", line 220 in _is_owned
File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/threading.py", line 227 in wait
File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/threading.py", line 421 in wait
File "<string>", line 23 in run
File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/threading.py", line 735 in _bootstrap_inner
File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/threading.py", line 708 in _bootstrap
Current thread XXX:
File "<string>", line 10 in dump
File "<string>", line 28 in <module>
1 file changed