[FE] Switch from using namespace.licensedFeatures to namespace.availableFeatures

In %18.1, we introduced the namespace.licensedFeatures field in GQL. It was noted that since not all of the fields in the type are necessarily licensed features (e.g. has_issue_date_filter_feature), a more appropriate name would be namespace.availableFeatures.

Shared in (internal) slack:

I see. So this isn't really just for licensed features it could be related to any kind of feature availability. Maybe we could rename it to availableFeatures instead

In %18.3, the backend introduced an alias which allows both namespace.licensedFeatures and namespace.availableFeatures to return the same object, with the list of features available on the namespace.

With this alias in place, the frontend can now switch to using namespace.availableFeatures to fetch this data