Update/Remove privacy level docs page

[humitos]

Although we are deprecating Privacy Levels in #2663 and #3781, we still expose the docs for this and it's completely broken and confuse our users.

https://docs.readthedocs.io/en/latest/privacy.html

I think we should take one of these actions:

1. remove that page completely
2. add a warning note saying that Privacy Levels are deprecated. Although, I think this doesn't make too much sense

Any action taken will need to write "a new documentation" page for the Corporate site, where these permission levels do work.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[dojutsu-user]

@humitos
I am +1 on the first option.
Just needed to know that does this issue needs to wait for some time or not?
I am interested in sending a PR for this.

[humitos]

We took a first step by removing the "Protected" level at #5833