Remove spurious libnetwork vendor entry.

Not sure how this got added in there...

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

vendor.conf

@@ -45,8 +45,6 @@ github.com/grpc-ecosystem/go-grpc-middleware        3c51f7f332123e8be5a157c0802a
 
 # libnetwork
 
-# When updating, also update LIBNETWORK_COMMIT in hack/dockerfile/install/proxy.installer accordingly
-github.com/docker/libnetwork                        64b7a4574d1426139437d20e81c0b6d391130ec8
 github.com/docker/go-events                         e31b211e4f1cd09aa76fe4ac244571fab96ae47f
 github.com/armon/go-radix                           e39d623f12e8e41c7b5529e9a9dd67a1e2261f80
 github.com/armon/go-metrics                         eb0af217e5e9747e41dd5303755356b62d28e3ec