Expand comment and remove unused imports.

game-app/game-core/src/main/java/games/strategy/triplea/delegate/AbstractPlaceDelegate.java

@@ -992,6 +992,8 @@ protected Collection<Unit> getUnitsToBePlaced(
     // Filter each type separately, since we don't want a max on one type to filter out all units of
     // another type, if the two types have a combined limit. UnitStackingLimitFilter doesn't do
     // that directly since other call sites (e.g. move validation) do need the combined filtering.
+    // But we need to do it this way here, since the result will be shown for choosing which units
+    // to build (where we want to show all the types that can be built).
     final var result = new ArrayList<Unit>();
     for (UnitType ut : UnitUtils.getUnitTypesFromUnitList(units)) {
       result.addAll(

game-app/game-core/src/test/java/games/strategy/triplea/delegate/PlaceDelegateTest.java

@@ -10,7 +10,6 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.hamcrest.Matchers.hasSize;
-import static org.hamcrest.Matchers.not;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 
@@ -19,7 +18,6 @@
 import games.strategy.engine.data.UnitType;
 import games.strategy.engine.delegate.IDelegateBridge;
 import games.strategy.triplea.delegate.data.PlaceableUnits;
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;