No difference reported for required property changed to optional

[mikekistler]

Openapi-diff does not report a required property that was changed to optional -- removed from the schema "required" array. Changing a required property to optional in an output schema could cause breaking changes if a client relies on a property always being present in a response (because it was marked "required") and the property is then omitted from some responses in the new version.

[jianyexi]

Thanks, and also optional changed to required