Fix flutter missing import

Author: abnegate

templates/flutter/lib/package.dart.twig

@@ -11,6 +11,7 @@ import 'src/enums.dart';
 import 'src/service.dart';
 import 'src/input_file.dart';
 import 'models.dart' as models;
+import 'enums.dart' as enums;
 import 'src/upload_progress.dart';
 
 export 'src/response.dart';

tests/languages/flutter/tests.dart

@@ -21,7 +21,7 @@ void main() async {
   PathProviderPlatform.instance = FakePathProvider();
   Client client = Client()
       .addHeader("Origin", "http://localhost")
-      .setSelfSigned(true);
+      .setSelfSigned();
   Foo foo = Foo(client);
   Bar bar = Bar(client);
   General general = General(client);