## 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/team.py
import re
from typing import Any, Dict, List, Optional
import pytz
from django.contrib.postgres.fields import ArrayField
from django.core.validators import MinLengthValidator
from django.db import models
from django.dispatch.dispatcher import receiver
from posthog.helpers.dashboard_templates import create_dashboard_from_template
from posthog.utils import GenericEmails
from .dashboard import Dashboard
from .utils import UUIDClassicModel, generate_random_token, sane_repr
TEAM_CACHE: Dict[str, "Team"] = {}
TIMEZONES = [(tz, tz) for tz in pytz.common_timezones]
DEPRECATED_ATTRS = (
    "plugins_opt_in",
    "opt_out_capture",
    "users",
    "event_names",
    "event_names_with_usage",
    "event_properties",
    "event_properties_with_usage",
    "event_properties_numerical",
)
class TeamManager(models.Manager):