## Bug description

personal_api_key.last_updated_at is updated every request with API keys.

This is one of the most time-consuming queries we do against postgres: https://metabase.posthog.net/question/344-most-time-consuming-postgres-queries


## Environment

- [x] PostHog Cloud
- [ ] self-hosted PostHog (ClickHouse-based), version/commit: _please provide_
- [ ] self-hosted PostHog (Postgres-based, legacy), version/commit: _please provide_

## Additional context

There's a half-hearted attempt at fixing this over at https://github.com/PostHog/posthog/pull/10383, but this was shot down due to UX concerns.

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

posthog/auth.py
cls,
        request: Union[HttpRequest, Request],
        request_data: Optional[Dict[str, Any]] = None,
        extra_data: Optional[Dict[str, Any]] = None,
    ) -> Optional[str]:
        """Try to find personal API key in request and return it."""
        key_with_source = cls.find_key_with_source(request, request_data, extra_data)
        return key_with_source[0] if key_with_source is not None else None
    @classmethod
    def authenticate(cls, request: Union[HttpRequest, Request]) -> Optional[Tuple[Any, None]]:
        personal_api_key_with_source = cls.find_key_with_source(request)
        if not personal_api_key_with_source:
            return None
        personal_api_key, source = personal_api_key_with_source
        PersonalAPIKey = apps.get_model(app_label="posthog", model_name="PersonalAPIKey")
        try:
            personal_api_key_object = (
                PersonalAPIKey.objects.select_related("user").filter(user__is_active=True).get(value=personal_api_key)
            )
        except PersonalAPIKey.DoesNotExist:
            raise AuthenticationFailed(detail=f"Personal API key found in request {source} is invalid.")
        personal_api_key_object.last_used_at = timezone.now()
        personal_api_key_object.save()
        assert personal_api_key_object.user is not None
        return personal_api_key_object.user, None
    @classmethod
    def authenticate_header(cls, request) -> str:
        return cls.keyword
class TemporaryTokenAuthentication(authentication.BaseAuthentication):