This reverts commit 3420a145, reversing
changes made to afb66a5a.

This method is repeatedly used throughout the docs (in the [AC::Connection docs](https://github.com/rails/rails/blob/12b684985837bc8ee9ad15c174cf4e07ca82d7c4/actioncable/lib/action_cable/connection/base.rb#L28), the [AC README](https://github.com/rails/rails/blob/12b684985837bc8ee9ad15c174cf4e07ca82d7c4/actioncable/README.md#a-full-stack-example), the [AC Guides](https://github.com/rails/rails/blob/12b684985837bc8ee9ad15c174cf4e07ca82d7c4/guides/source/action_cable_overview.md#connection-setup)), but not actually documented itself and seemingly not supported for public use based on its current `private` status.

This actually makes the method public and documents it.  The actual behavior that’s documented here is implemented [here](https://github.com/rails/rails/blob/12b684985837bc8ee9ad15c174cf4e07ca82d7c4/actioncable/lib/action_cable/connection/base.rb#L213-L219), via [this rescuing of the UnauthorizedError](https://github.com/rails/rails/blob/3dd1de8ba4d5862b01e7f5dd3878b21fd98b443b/actioncable/lib/action_cable/connection/base.rb#L172).

The method is [already tested here](https://github.com/rails/rails/blob/25473baf409185638073fe2f016f4b9dda284e50/actioncable/test/connection/authorization_test.rb#L17-L29).