MacOS: fixes memory management issue. closes #3807

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
(cherry picked from commit f4ffaf1a8845d590a0cef7c31309e94185a1be1c)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/macosx/simple_prefs.m

@@ -741,7 +741,6 @@ static inline void save_string_list( intf_thread_t * p_intf, id object, const ch
     if( p_stringobject )
     {
         config_PutPsz( p_intf, name, [p_stringobject UTF8String] );
-        [p_stringobject release];
     }
 }