## Bug description

I have lost edit permissions to a [dashboard I created](https://app.posthog.com/dashboard/28987), despite still being listed as the owner of the dashboard

## Expected behavior

I should still be able to edit the dashboard

## How to reproduce

I noticed this problem after adding a new insight, but this doesn't appear to be the cause of the issue. I've duplicated the dashboard to restore access and adding a new insight didn't appear to cause the issue 

## 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

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

posthog/api/dashboard.py
model = Dashboard
        fields = [
            "id",
            "name",
            "description",
            "pinned",
            "items",
            "created_at",
            "created_by",
            "is_shared",
            "share_token",
            "deleted",
            "creation_mode",
            "use_template",
            "use_dashboard",
            "filters",
            "tags",
            "restriction_level",
            "effective_restriction_level",
            "effective_privilege_level",
        ]
        read_only_fields = [
            "creation_mode",
            "effective_restriction_level",
        ]
    def create(self, validated_data: Dict, *args: Any, **kwargs: Any) -> Dashboard: