remove duplicate findBuildingDef from GameWorldView

GameWorldView::findBuildingDef was a byte-equivalent re-implementation of
BuildingsConfig::findBuildingDef. All call sites now use the config helper,
matching SelectedBuildingPanel and BlueprintPanel.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GH8ZMRY3vhxxXcaUxBqxkk

src/ui/GameWorldView.h

@@ -182,7 +182,6 @@ private:
     void     clampScroll();
 
     bool     isValidPlacement(BuildingType type, QPoint anchor, Rotation rot) const;
-    const BuildingDef* findBuildingDef(BuildingType type) const;
     std::optional<BuildingId> buildingAtTile(QPoint tile) const;
     std::optional<BuildingId> siteAtTile(QPoint tile) const;
     // Ids of all buildings and construction sites whose footprint intersects