chore: replace usages of obsolete twitch struct with backing field (#3614)

Co-authored-by: Felanbird <41973452+Felanbird@users.noreply.github.com>

src/widgets/FramelessEmbedWindow.cpp

@@ -49,7 +49,7 @@ bool FramelessEmbedWindow::nativeEvent(const QByteArray &eventType,
                 auto channelName = root.value("channel-name").toString();
 
                 this->split_->setChannel(
-                    getApp()->twitch2->getOrAddChannel(channelName));
+                    getApp()->twitch->getOrAddChannel(channelName));
             }
         }
     }