## 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
"""
    List of generic emails that we don't want to use to filter out test accounts.
    """
    def __init__(self):
        with open(get_absolute_path("helpers/generic_emails.txt"), "r") as f:
            self.emails = {x.rstrip(): True for x in f}
    def is_generic(self, email: str) -> bool:
        at_location = email.find("@")
        if at_location == -1:
            return False
        return self.emails.get(email[at_location + 1 :], False)
def get_available_timezones_with_offsets() -> Dict[str, float]:
    now = dt.datetime.now()
    result = {}
    for tz in pytz.common_timezones:
        offset = pytz.timezone(tz).utcoffset(now)
        if offset is None:
            continue
        offset_hours = int(offset.total_seconds()) / 3600
        result[tz] = offset_hours
    return result