Remove human phenotypes that are not a descendant of phenotypic abnormality

[bryanlaraway]

As part of the data pre-cleaning, need to remove any HPO terms from consideration that are not a descendant of phenotypic abnormality (inheritance, blood types, etc).

Steps:

• Can either parse HPO directly from the Monarch KG or alternatively could download the latest version of HPO.json file, the latter of which might be preferred.
• Generate the HPO graph and a list of descendants of phenotypic abnormality using NetworkX.
• Filter HPO terms from considered phenotypes that are not within that list of descendants.