Remove invalid code

adapter/v2ray.go

@@ -5,7 +5,6 @@ import (
 	"net"
 
 	E "github.com/sagernet/sing/common/exceptions"
-	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
 )
 
@@ -19,7 +18,6 @@ type V2RayServerTransport interface {
 type V2RayServerTransportHandler interface {
 	N.TCPConnectionHandler
 	E.Handler
-	FallbackConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error
 }
 
 type V2RayClientTransport interface {