API Deprecate some unused API

[GuySartorelli]

Description

Deprecates some API that isn't in use anywhere and has no clear purpose.

Issues

• Deprecate unused API related to subclass_access in DataObject #11109

Pull request checklist

• The target branch is correct
  • See picking the right version
• All commits are relevant to the purpose of the PR (e.g. no debug statements, unrelated refactoring, or arbitrary linting)
  • Small amounts of additional linting are usually okay, but if it makes it hard to concentrate on the relevant changes, ask for the unrelated changes to be reverted, and submitted as a separate PR.
• The commit messages follow our commit message guidelines
• The PR follows our contribution guidelines
• Code changes follow our coding conventions
• tests aren't necessary for this change
• Any relevant User Help/Developer documentation is updated; for impactful changes, information is added to the changelog for the intended release
• CI is green

[emteknetnz]

Merge on green