neon: use expand instead of reduce

packages/neon/neon/lib/src/app.dart

@@ -273,7 +273,7 @@ class _NeonAppState extends State<NeonApp> with WidgetsBindingObserver, tray.Tra
                       supportedLocales: {
                         ..._appImplementations
                             .map((final app) => app.supportedLocales)
-                            .reduce((final value, final element) => [...value, ...element]),
+                            .expand((final element) => element),
                         ...AppLocalizations.supportedLocales,
                       },
                       themeMode: themeMode,

packages/neon/neon/lib/src/utils/localizations.dart

@@ -5,7 +5,7 @@ part of '../../neon.dart';
 /// When the system locale is not supported [fallbackLocale] will be used.
 Future<AppLocalizations> appLocalizationsFromSystem([final Locale fallbackLocale = const Locale('en', 'US')]) async {
   final systemLocale = await findSystemLocale();
-  final parts = systemLocale.split('_').map((final a) => a.split('.')).reduce((final a, final b) => [...a, ...b]);
+  final parts = systemLocale.split('_').map((final a) => a.split('.')).expand((final e) => e).toList();
   final locale = Locale(parts[0], parts.length > 1 ? parts[1] : null);
 
   final isSupported = AppLocalizations.delegate.isSupported(locale);