Remove documentation key from metadata of private methods

[sbethur]

Description of issue

Metadata of many ~~private~~ non-public (private, codegen-only etc.) methods include documentation key like:

       'documentation': {
           'description': 'TBD'
       },

In some instances the content is TBD. Given the methods are private, we can remove the documentation key from metadata.

[texasaggie97-zz]

FYI: This may break codegen. It may expect ['documentation']['description'] to exist. It also may not break it...