rlp: using unsafe.Slice instead of SliceHeader (ethereum#29067)

Co-authored-by: Felix Lange <fjl@twurst.com>

rlp/unsafe.go

@@ -26,10 +26,5 @@ import (
 
 // byteArrayBytes returns a slice of the byte array v.
 func byteArrayBytes(v reflect.Value, length int) []byte {
-	var s []byte
-	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&s))
-	hdr.Data = v.UnsafeAddr()
-	hdr.Cap = length
-	hdr.Len = length
-	return s
+	return unsafe.Slice((*byte)(unsafe.Pointer(v.UnsafeAddr())), length)
 }