Remove extra cast

Author: HosseinYousefi

pkgs/jnigen/test/simple_package_test/runtime_test_registrant.dart

@@ -717,12 +717,12 @@ void registerTests(String groupName, TestRunnerCallback test) {
               final futureClass = JClass.forName('java/util/concurrent/Future');
               final getMethod =
                   futureClass.instanceMethodId('get', '()Ljava/lang/Object;');
-              final result = getMethod(future, JObject.type, []);
+              final result = getMethod(future, T, []);
               // A workaround for `--pause-isolates-on-exit`. Otherwise getting test
               // with coverage pauses indefinitely here.
               // https://github.com/dart-lang/coverage/issues/472
               Isolate.current.kill();
-              sendPort.send(result.castTo(T));
+              sendPort.send(result);
             }, receivePort.sendPort);
             return (await receivePort.first) as $T;
           }