remove getBoundingBoxAsset and destroyBoundingBoxAsset from ThermionAsset

thermion_dart/lib/src/filament/src/interface/asset.dart

@@ -101,24 +101,6 @@ abstract class ThermionAsset {
   /// [createBoundingBoxAsset] before this method.
   Future<Aabb3> getBoundingBox();
 
-  ///
-  /// The bounding box for this asset, as an actual renderable asset.
-  /// This is safe to call multiple times; if [boundingBoxAsset] is non-null,
-  /// this will simply return the existing bounding box asset.
-  ///
-  /// You will still need to call [Scene.add] to add this to the scene.
-  ///
-  Future<ThermionAsset> getBoundingBoxAsset() {
-    throw UnimplementedError();
-  }
-
-  ///
-  ///
-  ///
-  Future destroyBoundingBoxAsset(Scene scene) {
-    throw UnimplementedError();
-  }
-
   ///
   ///
   ///