Style skeleton button on import screen

editor/icons/SkeletonPreview.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16"><path fill="#eee" d="M6 2a4 4 0 0 0-2 7.453V13a2 2 0 0 0 2 2h4a2 2 0 0 0 2-2V9.453A4 4 0 0 0 10 2zM5 5a1 1 0 0 1 0 2 1 1 0 0 1 0-2zm6 0a1 1 0 0 1 0 2 1 1 0 0 1 0-2zM7 7h2v1H7zM5 9h1v1h1V9h2v1h1V9h1v4h-1v-1H9v1H7v-1H6v1H5V8z"/></svg>

editor/import/3d/scene_import_settings.cpp

@@ -1329,7 +1329,7 @@ void SceneImportSettingsDialog::_notification(int p_what) {
 			light_2_switch->set_button_icon(theme_cache.light_2_icon);
 			light_rotate_switch->set_button_icon(theme_cache.rotate_icon);
 
-			animation_toggle_skeleton_visibility->set_button_icon(get_editor_theme_icon(SNAME("Skeleton3D")));
+			animation_toggle_skeleton_visibility->set_button_icon(get_editor_theme_icon(SNAME("SkeletonPreview")));
 		} break;
 
 		case NOTIFICATION_PROCESS: {
@@ -1725,7 +1725,7 @@ SceneImportSettingsDialog::SceneImportSettingsDialog() {
 	animation_toggle_skeleton_visibility = memnew(Button);
 	animation_hbox->add_child(animation_toggle_skeleton_visibility);
 	animation_toggle_skeleton_visibility->set_toggle_mode(true);
-	animation_toggle_skeleton_visibility->set_flat(true);
+	animation_toggle_skeleton_visibility->set_theme_type_variation("FlatButton");
 	animation_toggle_skeleton_visibility->set_focus_mode(Control::FOCUS_NONE);
 	animation_toggle_skeleton_visibility->set_tooltip_text(TTR("Toggle Animation Skeleton Visibility"));