Bug 23651: Add address of restricted page to syspref description

Bug 23651: Add address of restricted page to syspref description

To test:
1 - Look at the restricted page syspref
2 - Check that the url is listed
3 - Add some content to the page
4 - Save the prefs
5 - Verify the address listed takes you to the page on the opac

Signed-off-by: Lisette Scheer <lisetteslatah@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit fa97bc90df532720287eaf296c15f7facdaa730d)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>