Bug 9958: Improve RoutingSerials sys pref description

Bug 9958: Improve RoutingSerials sys pref description

The RoutingSerials preference controls if the routing
list related functionality is visible in the serials
module.

To test:
- Go to the system preference editor - RoutingSerials
- Check the current description
- Apply patch
- Check the new description
- Verify functionality matches description

NOTE: The preference change is merely cosmetic. The value is
      still YesNo. A few git reset --hard origin/master
      and page refreshes confirmed expected values.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
(cherry picked from commit 90ebffcffae59b5ded2db3dce875be0293b845e1)
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>