metropolis/node/core/rpc: remove noop append

Change-Id: I9817807cf15c2f2b2a8ea6b8292a15e44cbdccb8
Reviewed-on: https://review.monogon.dev/c/monogon/+/2970
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
Tested-by: Jenkins CI
diff --git a/metropolis/node/core/rpc/client.go b/metropolis/node/core/rpc/client.go
index 8619d19..4b64654 100644
--- a/metropolis/node/core/rpc/client.go
+++ b/metropolis/node/core/rpc/client.go
@@ -94,7 +94,6 @@
 		Certificate: [][]byte{certificateBytes},
 		PrivateKey:  private,
 	}
-	opts = append(opts)
 	return NewAuthenticatedCredentials(certificate, opts...), nil
 }