fix(cloud_firestore): properly export pigeon message file from interface (#13316)

Co-authored-by: Russell Wheatley <russellwheatley85@gmail.com>

Author: ChristianEdwardPadilla

packages/cloud_firestore/cloud_firestore_platform_interface/lib/cloud_firestore_platform_interface.dart

@@ -9,7 +9,6 @@ import 'src/internal/pointer.dart';
 
 export 'package:collection/collection.dart' show ListEquality;
 
-export '/src/pigeon/messages.pigeon.dart';
 export 'src/blob.dart';
 export 'src/field_path.dart';
 export 'src/field_path_type.dart';
@@ -18,6 +17,7 @@ export 'src/geo_point.dart';
 export 'src/get_options.dart';
 export 'src/load_bundle_task_state.dart';
 export 'src/persistence_settings.dart';
+export 'src/pigeon/messages.pigeon.dart';
 export 'src/platform_interface/platform_interface_aggregate_query.dart';
 export 'src/platform_interface/platform_interface_aggregate_query_snapshot.dart';
 export 'src/platform_interface/platform_interface_collection_reference.dart';