Bug 31036: (QA follow-up) Add a warning to the system preference

Bug 31036: (QA follow-up) Add a warning to the system preference

As suggested by Katrin, adding a warning to the system preference that
this has an effect on SIP configurations that needs to be understood.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit f154fb0372d2e24318cad75bb65b993d47da8290)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
(cherry picked from commit 604da9beaaaaa90c875dfcc05261f45793b3fb7c)
Signed-off-by: Arthur Suzuki <arthur.suzuki@biblibre.com>