## 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
organization: models.ForeignKey = models.ForeignKey(
        "posthog.Organization", on_delete=models.CASCADE, related_name="teams", related_query_name="team"
    )
    api_token: models.CharField = models.CharField(
        max_length=200,
        unique=True,
        default=generate_random_token,
        validators=[MinLengthValidator(10, "Project's API token must be at least 10 characters long!")],
    )
    app_urls: ArrayField = ArrayField(models.CharField(max_length=200, null=True), default=list, blank=True)
    name: models.CharField = models.CharField(
        max_length=200, default="Default Project", validators=[MinLengthValidator(1, "Project must have a name!")],
    )
    slack_incoming_webhook: models.CharField = models.CharField(max_length=500, null=True, blank=True)
    created_at: models.DateTimeField = models.DateTimeField(auto_now_add=True)
    updated_at: models.DateTimeField = models.DateTimeField(auto_now=True)
    anonymize_ips: models.BooleanField = models.BooleanField(default=False)
    completed_snippet_onboarding: models.BooleanField = models.BooleanField(default=False)
    ingested_event: models.BooleanField = models.BooleanField(default=False)
    session_recording_opt_in: models.BooleanField = models.BooleanField(default=False)
    session_recording_retention_period_days: models.IntegerField = models.IntegerField(
        null=True, default=None, blank=True
    )
    signup_token: models.CharField = models.CharField(max_length=200, null=True, blank=True)
    is_demo: models.BooleanField = models.BooleanField(default=False)
    test_account_filters: models.JSONField = models.JSONField(default=list)