Cleanup: remove unused code from four files (#3234)

## Description:

PR 2/x in effort to break up PR
https://github.com/openfrontio/OpenFrontIO/pull/3220.

Removes unused code and properties.

- **Game.ts** and **DefaultConfig** unitInfo: removed
_canBuildTrainStation_ and _expirimental_ properties, as they weren't
used anywhere anymore.

- **PlayerActionHandler**: remove unused getPlayerActions, the only
potential caller MainRadialMenu already just calls myPlayer.actions via
GameView directly.

- **StructureIconsLayer**: remove unused PlayerActions

## 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:

tryout33

src/client/graphics/layers/PlayerActionHandler.ts

@@ -1,5 +1,4 @@
 import { EventBus } from "../../../core/EventBus";
-import { PlayerActions } from "../../../core/game/Game";
 import { TileRef } from "../../../core/game/GameMap";
 import { PlayerView } from "../../../core/game/GameView";
 import {
@@ -23,13 +22,6 @@ export class PlayerActionHandler {
     private uiState: UIState,
   ) {}
 
-  async getPlayerActions(
-    player: PlayerView,
-    tile: TileRef,
-  ): Promise<PlayerActions> {
-    return await player.actions(tile);
-  }
-
   handleAttack(player: PlayerView, targetId: string | null) {
     this.eventBus.emit(
       new SendAttackIntentEvent(