Fix button color for rate us dialog

lib/ui/settings/backup_section_widget.dart

@@ -300,9 +300,6 @@ class BackupSectionWidgetState extends State<BackupSectionWidget> {
         TextButton(
           child: Text(
             "Ok",
-            style: TextStyle(
-              color: Colors.white,
-            ),
           ),
           onPressed: () {
             showToast(