feat: removed unused permission events

[Zacharis278]

Description: These events were added in anticipation of the roles and permissions changes. That work is now on hold and we have instead opted to publish an event based on roles as they exist in edx-platform today. See https://github.com/openedx/openedx-events/pull/309. As written this event might not match the future state of that work if it is picked up again. I propose these definitions be removed to avoid confusion.

Reviewers:

• [ ] tag reviewer
• [ ] tag reviewer

Merge checklist:

• [ ] All reviewers approved
• [ ] CI build is green
• [ ] Version bumped
• [ ] Changelog record added
• [ ] Documentation updated (not only docstrings)
• [ ] Commits are squashed

Post merge:

• [ ] Create a tag
• [ ] Check new version is pushed to PyPI after tag-triggered build is finished.
• [ ] Delete working branch (if not needed anymore)

Author concerns: List any concerns about this PR - inelegant solutions, hacks, quick-and-dirty implementations, concerns about migrations, etc.

[mariajgrimaldi]

I'll look into the docs failure so we can merge this soon.