`test_query_trace_info.py`: adapt regex to NT path style

`test_query_trace_info.py`: adapt regex to NT path style

In a MinGW 64 test environment, the stream path is expressed using NT
path (`C:\\...`). In `test_query_trace_info.py`, adapt the regex
accordingly using Python's `pathlib` API.

Change-Id: Ieee3b9cac0881aec7086cef69ecf681ad71c0722
Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1708
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>