(PR#10346) [Bugfix] Correct add_to_size_limit check in city_desirability()

<URL: http://rt.freeciv.org/Ticket/Display.html?id=10346 >

> [marko.lindqvist-pL9mn150aekxHbG02/[email protected] - Sun Sep 26 15:16:17 2004]:
> 
> 
>   city_desirability() and test_unit_add_or_build_city() check 
> add_to_size_limit differently. city_desirability() checks if we have 
> already reached that limit and test_unit_add_or_build_city() checks if 
> we are going to get over limit. This makes a difference when 
> unit_pop_value > 1.
>   Attached patch makes check in city_desirability() similar to one in 
> test_unit_add_or_build_city().

Shouldn't city_desirability just call test_unit_add_or_build_city?

jason