src.ctf.fs: remove ctf_fs_trace_destroy

src.ctf.fs: remove ctf_fs_trace_destroy

Remove it and the custom deleter, since ctf_fs_trace instances can now
be simply deleted.

Change-Id: I59f3f89b4b3faee45b3708245242cee009d218b7
Reviewed-on: https://review.lttng.org/c/babeltrace/+/8287
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/12325
CI-Build: Simon Marchi <simon.marchi@efficios.com>
Tested-by: jenkins <jenkins@lttng.org>