Added missing from typing imports. (#8724)

certbot/tests/plugins/disco_test.py

@@ -2,6 +2,7 @@
 import functools
 import string
 import unittest
+from typing import List
 
 try:
     import mock

certbot/tests/plugins/selection_test.py

@@ -1,6 +1,7 @@
 """Tests for letsencrypt.plugins.selection"""
 import sys
 import unittest
+from typing import List
 
 try:
     import mock

certbot/tests/plugins/standalone_test.py

@@ -3,6 +3,7 @@
 import socket
 from socket import errno as socket_errors  # type: ignore
 import unittest
+from typing import Dict, Set, Tuple
 
 import josepy as jose
 try: