update dark mode bg3 color

frontend/app_flowy/lib/workspace/presentation/widgets/menu/widget/app/section/item.dart

@@ -43,7 +43,7 @@ class ViewSectionItem extends StatelessWidget {
           return InkWell(
             onTap: () => onSelected(context.read<ViewBloc>().state.view),
             child: FlowyHover(
-              config: HoverDisplayConfig(hoverColor: theme.bg2),
+              config: HoverDisplayConfig(hoverColor: theme.bg3),
               builder: (_, onHover) => _render(context, onHover, state, theme.iconColor),
               isOnSelected: () => state.isEditing || isSelected,
             ),

frontend/app_flowy/packages/flowy_infra/lib/theme.dart

@@ -129,7 +129,7 @@ class AppTheme {
           ..shader7 = _black
           ..bg1 = _black
           ..bg2 = _black
-          ..bg3 = _grey
+          ..bg3 = const Color(0xff4f4f4f)
           ..bg4 = const Color(0xff2c144b)
           ..tint1 = const Color(0xffc3adff)
           ..tint2 = const Color(0xffffadf9)