## 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/utils.py
import base64
import datetime
import datetime as dt
import gzip
import hashlib
import json
import os
import re
import subprocess
import time
import uuid
from itertools import count
from typing import (
    Any,
    Dict,
    Generator,
    List,
    Mapping,
    Optional,
    Tuple,
    Union,
)
from urllib.parse import urljoin, urlparse