trie: remove Key in MissingNodeError

The key was constructed from nibbles, which isn't possible for all
nodes. Remove the only use of Key in LightTrie by always retrying with
the original key that was looked up.

trie/trie.go

@@ -450,7 +450,6 @@ func (t *Trie) resolveHash(n hashNode, prefix, suffix []byte) (node, error) {
 		return nil, &MissingNodeError{
 			RootHash:  t.originalRoot,
 			NodeHash:  common.BytesToHash(n),
-			Key:       compactHexEncode(append(prefix, suffix...)),
 			PrefixLen: len(prefix),
 			SuffixLen: len(suffix),
 		}