## Bug description

Deprecation warning due to invalid escape sequences in Python 3.8 . 

```
posthog/models/team.py:47:46: W605 invalid escape sequence '\w'
posthog/models/filters/test/test_filter.py:131:74: W605 invalid escape sequence '\.'
posthog/models/filters/test/test_filter.py:135:78: W605 invalid escape sequence '\.'
posthog/migrations/0132_team_test_account_filters.py:51:46: W605 invalid escape sequence '\w'
ee/clickhouse/views/element.py:47:48: W605 invalid escape sequence '\.'
ee/clickhouse/views/element.py:50:69: W605 invalid escape sequence '\.'
```

This is little more important since Python emits deprecation warning during compile time for these

## Expected behavior

This can be fixed with pyupgrade : https://github.com/asottile/pyupgrade#invalid-escape-sequences . Appropriate rule can be added to flake8 so that this caught.

## How to reproduce


```
find posthog -iname '*py' | xargs -P4 -I{} python3.8 -Wall -m py_compile {}     
posthog/models/team.py:47: DeprecationWarning: invalid escape sequence \w
  example_email = re.search("@[\w.]+", example_emails[0])
posthog/models/filters/test/test_filter.py:131: DeprecationWarning: invalid escape sequence \.
  filter = Filter(data={"properties": {"$current_url__regex": "\.com$"}})
posthog/models/filters/test/test_filter.py:135: DeprecationWarning: invalid escape sequence \.
  filter = Filter(data={"properties": {"$current_url__not_regex": "\.eee$"}})
posthog/migrations/0132_team_test_account_filters.py:51: DeprecationWarning: invalid escape sequence \w
  example_email = re.search("@[\w.]+", example_emails[0])
```

## Environment

- [ ] PostHog Cloud
- [ ] self-hosted PostHog, version/commit: _please provide_

## Additional context



#### *Thank you* for your bug report – we love squashing them!

posthog/models/filters/test/test_filter.py
def test_old_style_properties(self):
        filter = Filter(data={"properties": {"$browser__is_not": "IE7", "$OS": "Mac",}})
        self.assertEqual(filter.properties[0].key, "$browser")
        self.assertEqual(filter.properties[0].operator, "is_not")
        self.assertEqual(filter.properties[0].value, "IE7")
        self.assertEqual(filter.properties[0].type, "event")
        self.assertEqual(filter.properties[1].key, "$OS")
        self.assertEqual(filter.properties[1].operator, None)
        self.assertEqual(filter.properties[1].value, "Mac")
    def test_to_dict(self):
        filter = Filter(
            data={
                "events": [{"id": "$pageview"}],
                "display": "ActionsLineGraph",
                "compare": True,
                "interval": "",
                "actions": [],
                "date_from": "2020-01-01T20:00:00Z",
            }
        )
        self.assertCountEqual(
            list(filter.to_dict().keys()),
            ["events", "display", "compare", "insight", "date_from", "funnel_window_days",],
        )
def property_to_Q_test_factory(filter_events: Callable, event_factory, person_factory):
    class TestPropertiesToQ(BaseTest):