rlp: remove workaround for Value.Bytes (ethereum#32433)

As of Go 1.19, it is permitted to call Bytes() on a reflect.Value
representing an adressable byte array. So we can remove our workaround,
undoing ethereum#22924.

https://go.dev/doc/go1.19#reflectpkgreflect

> The method [Value.Bytes](https://go.dev/pkg/reflect/#Value.Bytes) now
accepts addressable arrays in addition to slices.

Author: fjl

rlp/decode.go

@@ -371,7 +371,7 @@ func decodeByteArray(s *Stream, val reflect.Value) error {
 	if err != nil {
 		return err
 	}
-	slice := byteArrayBytes(val, val.Len())
+	slice := val.Bytes()
 	switch kind {
 	case Byte:
 		if len(slice) == 0 {

rlp/encode.go

@@ -240,7 +240,6 @@ func makeByteArrayWriter(typ reflect.Type) writer {
 	case 1:
 		return writeLengthOneByteArray
 	default:
-		length := typ.Len()
 		return func(val reflect.Value, w *encBuffer) error {
 			if !val.CanAddr() {
 				// Getting the byte slice of val requires it to be addressable. Make it
@@ -249,7 +248,7 @@ func makeByteArrayWriter(typ reflect.Type) writer {
 				copy.Set(val)
 				val = copy
 			}
-			slice := byteArrayBytes(val, length)
+			slice := val.Bytes()
 			w.encodeStringHeader(len(slice))
 			w.str = append(w.str, slice...)
 			return nil