Fix pop being applied while city is Under Construction (#3655)

## Description:

Fixes population from a city being applied as soon as it is placed
instead of when it is fully built

## Please complete the following:

- [X] I have added screenshots for all UI updates
- [X] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [X] I have added relevant tests to the test directory
- [X] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

babyboucher

src/core/configuration/DefaultConfig.ts

@@ -771,6 +771,7 @@ export class DefaultConfig implements Config {
         : 2 * (Math.pow(player.numTilesOwned(), 0.6) * 1000 + 50000) +
           player
             .units(UnitType.City)
+            .filter((u) => !u.isUnderConstruction())
             .map((city) => city.level())
             .reduce((a, b) => a + b, 0) *
             this.cityTroopIncrease();