fix analyzer issues

Author: denrase

flutter/lib/src/sentry_flutter_options.dart

@@ -1,5 +1,4 @@
 import 'dart:async';
-import 'dart:ui';
 
 import 'package:file/file.dart';
 import 'package:file/local.dart';
@@ -8,7 +7,6 @@ import 'package:flutter/widgets.dart';
 import 'package:meta/meta.dart' as meta;
 import 'package:sentry/sentry.dart';
 
-import '../sentry_flutter.dart';
 import 'binding_wrapper.dart';
 import 'event_processor/screenshot_event_processor.dart';
 import 'navigation/time_to_display_tracker.dart';