Update dependency freezed to v4

Author: renovate[bot]

frontend/pubspec.yaml

@@ -72,7 +72,7 @@ dev_dependencies:
   build_runner: ^2.14.1
   riverpod_lint: ^3.1.0
   json_serializable: ^6.9.0
-  freezed: ^3.0.0
+  freezed: ^4.0.0
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec