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.

requirements_for_test.txt

@@ -2,7 +2,7 @@
 flake8==3.8.4
 flake8-bugbear==20.11.1
 isort==5.7.0
-moto==1.3.16
+moto==2.0.11
 pytest==6.1.2
 pytest-env==0.6.2
 pytest-mock==3.3.1

tests/app/celery/test_scheduled_tasks.py

@@ -1,10 +1,10 @@
 from collections import namedtuple
 from datetime import datetime, timedelta
+from unittest import mock
 from unittest.mock import call
 
 import pytest
 from freezegun import freeze_time
-from mock import mock
 
 from app.celery import scheduled_tasks
 from app.celery.scheduled_tasks import (

tests/app/dao/test_fact_notification_status_dao.py

@@ -1,7 +1,7 @@
 from datetime import date, datetime, time, timedelta
+from unittest import mock
 from uuid import UUID
 
-import mock
 import pytest
 from freezegun import freeze_time
 

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