Request fewer transfer journeys

The default is 12 per backend, which is rarely needed. And more can always
be requested in the UI anyway.

src/app/transfermanager.cpp

@@ -509,6 +509,7 @@ KPublicTransport::JourneyRequest TransferManager::journeyRequestForTransfer(cons
     req.setDownloadAssets(true);
     req.setIncludeIntermediateStops(true);
     req.setIncludePaths(true);
+    req.setMaximumResults(6);
     return req;
 }