Move to Flutter 3.47, use the improvements that come with this (#64)

Reviewed-on: #64

lib/models/requests/get_related_events.dart

@@ -1,14 +1,16 @@
 import "package:freezed_annotation/freezed_annotation.dart";
+
 part "get_related_events.freezed.dart";
 part "get_related_events.g.dart";
 
-@freezed
-abstract class GetRelatedEventsRequest with _$GetRelatedEventsRequest {
-  const factory GetRelatedEventsRequest({
-    required String roomId,
-    required String eventId,
-    required String relationType,
-  }) = _GetRelatedEventsRequest;
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable()
+class const GetRelatedEventsRequest({
+  required final String roomId,
+  required final String eventId,
+  required final String relationType,
+}) with _$GetRelatedEventsRequest {
+  Map<String, Object?> toJson() => _$GetRelatedEventsRequestToJson(this);
 
   factory GetRelatedEventsRequest.fromJson(Map<String, Object?> json) =>
       _$GetRelatedEventsRequestFromJson(json);