lib: remove unused internal component destroy functions

lib: remove unused internal component destroy functions

These destroy functions are empty, remove them.  They can always be
added back later if needed, but I don't see the value in keeping then
"just in case".

Change-Id: I5845d2834294583367c85a840b016a536bf0b120
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/11205
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>