In #33418, documentation from `ActionView::Helpers::RenderingHelper#render`
was copied to `ActionController::Renderer#render` with the intention of
documenting `ActionController::Rendering#render`.  Since then, further
documentation has been added to `ActionController::Renderer#render`, and
`ActionController::Renderer#render` has been mistaken for
`ActionController::Rendering#render` (for example, in #46045).

This commit adds documentation to `ActionController::Rendering#render`
(which was previously `:nodoc:` because it is a simple override of
`AbstractController::Rendering#render`), and updates related
documentation to point to `ActionController::Rendering#render`.

(cherry picked from commit aaf7bed0)