Add backward compatibility to WP_REST_Server::check_authentication()

[brbrr]

#46907 changed the public method signature for WP_REST_Server::check_authentication() which breaks backward compatibility.

We should switch to an optional parameter in check_authentication to make sure the method works in older versions

[ocean90]

Hello @brbrr, welcome to WordPress Trac!

Thanks for your report. I'm closing it as a duplicate of #46907 to keep the discussion at one place.