Codechange: make explicit when a TileIndex is cast to its basetype (#11190)

This prevents people accidentially assigning a TileIndex to a Date
or any other type they shouldn't.

src/story.cpp

@@ -99,7 +99,7 @@ static void UpdateElement(StoryPageElement &pe, TileIndex tile, uint32_t referen
 			break;
 		case SPET_LOCATION:
 			pe.text = text;
-			pe.referenced_id = tile;
+			pe.referenced_id = static_cast<uint32_t>(tile);
 			break;
 		case SPET_GOAL:
 			pe.referenced_id = (GoalID)reference;