fix: disable toolbar hover color

frontend/app_flowy/packages/appflowy_editor/lib/src/render/toolbar/toolbar_item_widget.dart

@@ -25,6 +25,7 @@ class ToolbarItemWidget extends StatelessWidget {
         child: MouseRegion(
           cursor: SystemMouseCursors.click,
           child: IconButton(
+            hoverColor: Colors.transparent,
             highlightColor: Colors.transparent,
             padding: EdgeInsets.zero,
             icon: item.iconBuilder(isHighlight),