all: remove redundant conversions and import names (#21903)

trie/database.go

@@ -100,7 +100,7 @@ func (n rawNode) cache() (hashNode, bool)   { panic("this should never end up in
 func (n rawNode) fstring(ind string) string { panic("this should never end up in a live trie") }
 
 func (n rawNode) EncodeRLP(w io.Writer) error {
-	_, err := w.Write([]byte(n))
+	_, err := w.Write(n)
 	return err
 }
 

trie/iterator.go

@@ -173,7 +173,7 @@ func (it *nodeIterator) LeafKey() []byte {
 func (it *nodeIterator) LeafBlob() []byte {
 	if len(it.stack) > 0 {
 		if node, ok := it.stack[len(it.stack)-1].node.(valueNode); ok {
-			return []byte(node)
+			return node
 		}
 	}
 	panic("not at leaf")