featureCompatibilityVersion field should be added to Cloud/Ops Manager Public API docs for the Automation resource

It looks like we forgot to add the new "featureCompatibilityVersion" field to the API docs for 3.4.

For 3.4 processes, the Process section should have the field "featureCompatibilityVersion" that may be set to "3.2" or "3.4" for MongoDB 3.4 processes, and null otherwise.