## 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
person1 = person_factory(
                team_id=self.team.pk, distinct_ids=["team_member"], properties={"email": "test@posthog.com"}
            )
            person1 = person_factory(
                team_id=self.team.pk, distinct_ids=["random_user"], properties={"email": "test@gmail.com"}
            )
            self.team.test_account_filters = [
                {"key": "email", "value": "@posthog.com", "operator": "not_icontains", "type": "person"}
            ]
            self.team.save()
            event_factory(team=self.team, distinct_id="team_member", event="$pageview")
            event_factory(team=self.team, distinct_id="random_user", event="$pageview")
            filter = Filter(data={FILTER_TEST_ACCOUNTS: True, "events": [{"id": "$pageview"}]})
            events = filter_events(filter=filter, team=self.team, person_query=True)
            self.assertEqual(len(events), 1)
    return TestPropertiesToQ
def _filter_events(filter: Filter, team: Team, person_query: Optional[bool] = False, order_by: Optional[str] = None):
    events = Event.objects
    if person_query:
        events = events.add_person_id(team.pk)
    events = events.filter(
        properties_to_Q(filter.properties, team_id=team.pk, filter_test_accounts=filter.filter_test_accounts)
    )
    events = events.filter(team_id=team.pk)
    if order_by:
        events = events.order_by(order_by)
    return events.values()
class TestDjangoPropertiesToQ(property_to_Q_test_factory(_filter_events, Event.objects.create, Person.objects.create)):  
    def test_person_cohort_properties(self):