UI: Fix incompatible settings message when streaming Multitrack Video

When streaming with Multitrack Video (Enhanced Broadcasting) and
incompatible settings, the warning message was missing parts of the
string due to incorrect translation string keys.

Additionally, use Unicode arrows to direct users through UI elements.

UI/multitrack-video-output.cpp

@@ -398,9 +398,9 @@ void MultitrackVideoOutput::PrepareStreaming(
 	auto multitrack_video_name =
 		QTStr("Basic.Settings.Stream.MultitrackVideoLabel");
 	if (obs_data_has_user_value(service_settings,
-				    "ertmp_multitrack_video_name")) {
+				    "multitrack_video_name")) {
 		multitrack_video_name = obs_data_get_string(
-			service_settings, "ertmp_multitrack_video_name");
+			service_settings, "multitrack_video_name");
 	}
 
 	auto auto_config_url_data = auto_config_url.toUtf8();
@@ -637,7 +637,7 @@ bool MultitrackVideoOutput::HandleIncompatibleSettings(
 			QString(" %1. %2\n").arg(num).arg(QTStr(name));
 
 		where_to_disable +=
-			QString(" %1. [%2 > %3 > %4]\n")
+			QString(" %1. [%2 → %3 → %4]\n")
 				.arg(num)
 				.arg(QTStr("Settings"))
 				.arg(QTStr("Basic.Settings.Advanced"))
@@ -667,12 +667,11 @@ bool MultitrackVideoOutput::HandleIncompatibleSettings(
 	QMessageBox mb(parent);
 	mb.setIcon(QMessageBox::Critical);
 	mb.setWindowTitle(QTStr("MultitrackVideo.IncompatibleSettings.Title"));
-	mb.setText(
-		QString(QTStr("MultitrackVideo.IncompatibleSettings.Text"))
-			.arg(obs_data_get_string(service_settings,
-						 "ertmp_multitrack_video_name"))
-			.arg(incompatible_settings)
-			.arg(where_to_disable));
+	mb.setText(QString(QTStr("MultitrackVideo.IncompatibleSettings.Text"))
+			   .arg(obs_data_get_string(service_settings,
+						    "multitrack_video_name"))
+			   .arg(incompatible_settings)
+			   .arg(where_to_disable));
 	auto this_stream = mb.addButton(
 		QTStr("MultitrackVideo.IncompatibleSettings.DisableAndStartStreaming"),
 		QMessageBox::AcceptRole);