[gendoc] Doc generation error for Required fields of subelements

[mbroz2]

Describe the bug
It seems as though for subelements, we don't include the Required in the Type field for required elements.  For example for keyStoreRef, it's correctly marked as required in the metatype.xml:
https://github.com/OpenLiberty/open-liberty/blob/78825b4dda1c5398bf3d8d165045742b5[…]afd/dev/com.ibm.ws.ssl/resources/OSGI-INF/metatype/metatype.xml

however, the generated adoc does not include the Required in the Type field:
https://github.com/OpenLiberty/docs-generated/blob/6710a0db0f447ec286a7458433258f774fda1d97/modules/reference/pages/config/ssl.adoc?plain=1#L62

This results with the published docs to fail to correctly flag those elements as required:
https://openliberty.io/docs/latest/reference/config/ssl.html#ssl.html#keyStore