source-dialog: add GOA sources to the list

Actually, it *should* add GOA sources,
don't know why I removed it.

src/gcal-source-dialog.c

@@ -240,7 +240,7 @@ add_source (GcalManager *manager,
         contains_source = TRUE;
     }
 
-  if (!contains_source && !is_goa_source (GCAL_SOURCE_DIALOG (user_data), source))
+  if (!contains_source)
     {
       GtkWidget *row;