rename none to null

std/hashmap/hashmap.hon

@@ -56,14 +56,14 @@ get func(
 	map @HashMap(K, V, hash_key, keys_eql),
 	key K,
 ) ?V {
-	if (map.count == 0) return none
+	if (map.count == 0) return null
 
 	hash :: normalize(hash_key(key))
 	idx usize = hash & (map.entries.len - 1)
 
 	while true {
 		entry :: map.entries[idx]
-		if (entry.hash == 0) return none
+		if (entry.hash == 0) return null
 
 		if (entry.hash == hash and keys_eql(entry.key, key)) {
 			return entry.value