wip: fix lint issues

Author: lijy91

packages/flutter_app_builder/lib/src/commands/flutter.dart

@@ -28,7 +28,8 @@ class FlutterVersion {
       engineRevision: json['engineRevision'] as String?,
       dartSdkVersion: json['dartSdkVersion'] as String?,
       devToolsVersion: json['devToolsVersion'] as String?,
-      flutterVersion: json['flutterVersion'] as String? ?? (json['frameworkVersion'] as String?),
+      flutterVersion: json['flutterVersion'] as String? ??
+          (json['frameworkVersion'] as String?),
     );
   }