pass code over pyupgrade --py39

Currently minum version supported python bersion is 3.9.
Pass code over `pyupgrade --py39`.

Signed-off-by: Tomasz Kłoczko <kloczek@github.com>

secretstorage/collection.py

@@ -16,7 +16,8 @@
 collections.
 """
 
-from typing import Iterator, Optional
+from typing import Optional
+from collections.abc import Iterator
 from jeepney.io.blocking import DBusConnection
 from secretstorage.defines import SS_PREFIX, SS_PATH
 from secretstorage.dhcrypto import Session