Bump moto version to try solve dependencies version conflict

Also update mock import statements in some test files as they
stopped working with this dependency update.

tests/app/user/test_rest.py

@@ -1,8 +1,8 @@
 import json
 import uuid
 from datetime import datetime
+from unittest import mock
 
-import mock
 import pytest
 from flask import current_app, url_for
 from freezegun import freeze_time