chore: remove Singleton & replace getIApp with getApp (#5514)

src/singletons/Toasts.cpp

@@ -35,7 +35,7 @@ using namespace literals;
 QString avatarFilePath(const QString &channelName)
 {
     // TODO: cleanup channel (to be used as a file) and use combinePath
-    return getIApp()->getPaths().twitchProfileAvatars % '/' % channelName %
+    return getApp()->getPaths().twitchProfileAvatars % '/' % channelName %
            u".png";
 }
 
@@ -74,7 +74,7 @@ bool Toasts::isEnabled()
 {
 #ifdef Q_OS_WIN
     return WinToast::isCompatible() && getSettings()->notificationToast &&
-           !(getIApp()->getStreamerMode()->isEnabled() &&
+           !(getApp()->getStreamerMode()->isEnabled() &&
              getSettings()->streamerModeSuppressLiveNotifications);
 #else
     return false;