message: Fix a java global reference leak
  We were acquiring a reference twice by accident.
  Fix
diff: @@ -86,7 +86,6 @@ JniBufferCallback::JniBufferCallback(JNIEnv* env, jobject handler, jobject callb
  AutoBuffer&& buffer)
  : JniCallback(env, handler, callback),
  mBuffer(std::move(buffer)) {
  - acquireCallbackJni(env, mCallbackUtils);
  }
  JniBufferCallback::~JniBufferCallback() = default;
  @@ -109,7 +108,6 @@ JniImageCallback* JniImageCallback::make(filament::Engine*,
  JniImageCallback::JniImageCallback(JNIEnv* env, jobject handler, jobject callback, long image)
  : JniCallback(env, handler, callback),
  mImage(image) {
  - acquireCallbackJni(env, mCallbackUtils);
  }
  JniImageCallback::~JniImageCallback() = default;
  