Remove unimplemented SceneAnimationImport plugin from menu

The code structure is still available if someone wanted to implement it.
Issue #3667 will be kept as a reminder for the added todo.

tools/editor/editor_node.cpp

@@ -5880,7 +5880,8 @@ EditorNode::EditorNode() {
 //	Ref<EditorSceneImporterFBXConv> _fbxconv_import = memnew( EditorSceneImporterFBXConv);
 //	_scene_import->add_importer(_fbxconv_import);
 	editor_import_export->add_import_plugin( _scene_import);
-	editor_import_export->add_import_plugin( Ref<EditorSceneAnimationImportPlugin>( memnew(EditorSceneAnimationImportPlugin(this))));
+	// TODO: This plugin has no code, it should be either implemented or dropped (GH-3667)
+	// editor_import_export->add_import_plugin( Ref<EditorSceneAnimationImportPlugin>( memnew(EditorSceneAnimationImportPlugin(this))));
 	editor_import_export->add_import_plugin( Ref<EditorMeshImportPlugin>( memnew(EditorMeshImportPlugin(this))));
 	editor_import_export->add_import_plugin( Ref<EditorFontImportPlugin>( memnew(EditorFontImportPlugin(this))));
 	editor_import_export->add_import_plugin( Ref<EditorSampleImportPlugin>( memnew(EditorSampleImportPlugin(this))));