Fix: integer-range-set.hpp: calling `_get_ref()` rather than `_put_ref()`

Fix: integer-range-set.hpp: calling `_get_ref()` rather than `_put_ref()`

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: Ic7c381d7dd7f2c5780f7678e48b76d23e8f3ca00
Reviewed-on: https://review.lttng.org/c/babeltrace/+/8183
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/10827
CI-Build: Philippe Proulx <eeppeliteloop@gmail.com>
Tested-by: jenkins <jenkins@lttng.org>