networks/Manifest.py: removed arria10_gx stuff

platform/altera/networks/Manifest.py

 def __helper():
   files = [ "altera_networks_pkg.vhd" ]
-  if syn_device[:2] == "10":     files.extend(["arria10gx_networks.qip"])
   if syn_device[:1] == "5":      files.extend(["arria5_networks.qip"])
   if syn_device[:6] == "ep2agx": files.extend(["arria2gx_networks.qip"])
   return files