tests: bt2: remove test_clock_class_priority_map.py

tests: bt2: remove test_clock_class_priority_map.py

The clock class priority map concept does not exist anymore and all the
testcases were marked as `skip` since then.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: Ib8e7d03662420f02446c5f901e86cf89fe09a09a
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1702
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>