UI: Add Restream.io bandwidth test stream key param

Allows testing bandwidth via streaming without the stream activating
remotely for viewers.

UI/window-basic-auto-config-test.cpp

@@ -218,6 +218,9 @@ void AutoConfigTestPage::TestBandwidthThread()
 		   wiz->serviceName == "Restream.io - RTMP") {
 		string_depad_key(key);
 		key += "?test=true";
+	} else if (wiz->serviceName == "Restream.io - FTL") {
+		string_depad_key(key);
+		key += "?test";
 	}
 
 	obs_data_set_string(service_settings, "service",