Remove unnecessary prefs

lib/core/prefs/general_prefs.dart

@@ -1,17 +1,3 @@
-import 'package:freezed_annotation/freezed_annotation.dart';
+import 'package:hiddify/utils/pref_notifier.dart';
 
-part 'general_prefs.freezed.dart';
-part 'general_prefs.g.dart';
-
-@freezed
-class GeneralPrefs with _$GeneralPrefs {
-  const GeneralPrefs._();
-
-  const factory GeneralPrefs({
-    // desktop only
-    @Default(false) bool silentStart,
-  }) = _GeneralPrefs;
-
-  factory GeneralPrefs.fromJson(Map<String, dynamic> json) =>
-      _$GeneralPrefsFromJson(json);
-}
+final silentStartProvider = PrefNotifier.provider("silent_start", false);