revert: feat add url for creating account on login page

SoObjects/SOGo/SOGoSystemDefaults.m

@@ -1157,11 +1157,6 @@ NSComparisonResult languageSort(id el1, id el2, void *context)
   return disableExport;
 }
 
-- (NSString *)urlCreateAccount
-{
-  return [self stringForKey: @"SOGoURLCreateAccount"];
-}
-
 - (BOOL) enableMailCleaning
 {
   return [self boolForKey: @"SOGoEnableMailCleaning"];