pav:lastUpdatedOn s/b pav:lastUpdateOn

[pboisver]

Check pav terms against https://pav-ontology.github.io/pav/

example: causal_pathways/goal_loss.json

Also, we probably don't need to (re)define terms in the @context, unless we are using them in a way that is not specified by the ontology or is different.

Recommend generally rechecking the terms and @contexts for the KB artifacts. See #230