## Bug description

Creating a selector with an attribute isn't working at all.

`[data-attr="bla"]`

## Expected behavior

It should work

## How to reproduce

1. Create action
2. Add an attribute in the selector
3. 


## Additional context

The reason for this is that we store the attributes as `attr__data-attr` but we do not add `attr__` in the filtering. I am working on a solution.


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

posthog/models/event.py
groups = ElementGroup.objects.filter(team_id=team_id)
        if filters.get("selector"):
            selector = Selector(filters["selector"])
            subqueries, filter = self._element_subquery(selector)
            groups = groups.annotate(**subqueries)  
        else:
            filter = {}
        for key in ["tag_name", "text", "href"]:
            if filters.get(key):
                filter["element__{}".format(key)] = filters[key]
        if not filter:
            return {}
        groups = groups.filter(**filter)
        return {"elements_hash__in": groups.values_list("hash", flat=True)}
    def filter_by_url(self, action_step: ActionStep, subquery: QuerySet):