## 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/migrations/0132_team_test_account_filters.py
at_location = email.find("@")
        if at_location == -1:
            return False
        return self.emails.get(email[at_location + 1 :], False)
def forward(apps, schema_editor):
    Team = apps.get_model("posthog", "Team")
    for team in Team.objects.all():
        filters = [
            {
                "key": "$host",
                "operator": "is_not",
                "value": ["localhost:8000", "localhost:5000", "127.0.0.1:8000", "127.0.0.1:3000"],
            },
        ]
        if team.organization:
            example_emails = team.organization.members.only("email")
            generic_emails = GenericEmails()
            example_emails = [email.email for email in example_emails if not generic_emails.is_generic(email.email)]
            if len(example_emails) > 0:
                example_email = re.search("@[\w.]+", example_emails[0])
                if example_email:
                    filters += [
                        {"key": "email", "operator": "not_icontains", "value": example_email.group(), "type": "person"},
                    ]
        team.test_account_filters = filters
        team.save()
def reverse(apps, schema_editor):
    pass
class Migration(migrations.Migration):