parent_osm_id should have a parent_osm_ids

[taylor.smock]

I'm in the process of writing a validator to find mistagged roundabouts (e.g., two roads come in at the same node) and that works, if and only if the names of the roads are different. Ideally, I would just run a count(parent_osm_ids) since those *are* guaranteed to be different.

Example of my code:

way[junction=roundabout][name] > node {set .is_in_named_roundabout}
node.is_in_roundabout!.is_in_named_roundabout[count(parent_tags("name")) > 1],
node.is_in_roundabout.is_in_named_roundabout[count(parent_tags("name")) > 2] {
        throwWarning: tr("Roundabouts should not have more than two additional ways at any node ({0})", parent_tags("name"));
}