## Bug description

There seems to be an issue with `get_available_timezones_with_offsets`, not sure at what point it broke.

```
Traceback (most recent call last):
    response = view_func(request, *args, **kwargs)
  File "/posthog/posthog/views.py", line 184, in preflight_check
    "available_timezones": get_available_timezones_with_offsets(),
    raise NonExistentTimeError(dt)
```

## Expected behavior
Preflight should work and the timezone list be returned correctly.


## How to reproduce

1. Just check `/_preflight` request

## Environment

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

## Additional context

Tagging @Twixes as you have more context on this.

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

posthog/test/test_utils.py
from django.test import TestCase
from freezegun import freeze_time
from posthog.utils import mask_email_address, relative_date_parse
class TestGeneralUtils(TestCase):
    def test_mask_email_address(self):
        self.assertEqual(mask_email_address("hey@posthog.com"), "h*y@posthog.com")
        self.assertEqual(mask_email_address("richard@gmail.com"), "r*****d@gmail.com")
        self.assertEqual(
            mask_email_address("m@posthog.com"), "*@posthog.com"
        )  
        self.assertEqual(mask_email_address("test+alias@posthog.com"), "t********s@posthog.com")
        with self.assertRaises(ValueError) as e:
            mask_email_address("not an email")
        self.assertEqual(str(e.exception), "Please provide a valid email address.")
class TestRelativeDateParse(TestCase):