Remove unused imports

lib/utils/file_sync_util.dart

@@ -1,7 +1,5 @@
-import 'dart:convert';
 import 'dart:math';
 
-import 'package:collection/collection.dart';
 import 'package:computer/computer.dart';
 import 'package:logging/logging.dart';
 import 'package:photo_manager/photo_manager.dart';