encoding/gob: remove always false comparison

This is not a functional change. nr is a uint64 and can never be less
than zero, remove the no-op comparison.

Fixes #11279

Change-Id: Iebb36cc8fe97428b503e65d01b5e67d2b2bc7369
Reviewed-on: https://go-review.googlesource.com/13876
Run-TryBot: Todd Neal <todd@tneal.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/encoding/gob/decode.go

@@ -634,7 +634,7 @@ func (dec *Decoder) ignoreSlice(state *decoderState, elemOp decOp) {
 func (dec *Decoder) decodeInterface(ityp reflect.Type, state *decoderState, value reflect.Value) {
 	// Read the name of the concrete type.
 	nr := state.decodeUint()
-	if nr < 0 || nr > 1<<31 { // zero is permissible for anonymous types
+	if nr > 1<<31 { // zero is permissible for anonymous types
 		errorf("invalid type name length %d", nr)
 	}
 	if nr > uint64(state.b.Len()) {