fix the timestamp changing between when a comment updates

opentech/apply/activity/messaging.py

...ly/activity/migrations/0022_add_versioning_to_comments.py

opentech/apply/activity/models.py

opentech/apply/activity/tests/factories.py

opentech/apply/activity/views.py

opentech/apply/determinations/views.py

opentech/apply/funds/serializers.py

opentech/apply/funds/tests/test_api_views.py