text: Title: Update HTTP status code constants wrt RFC 9110
  Body: Update our HTTP status code constants (in [`falcon/status_codes.py`](https://github.com/falconry/falcon/blob/master/falcon/status_codes.py)) to conform to [RFC 9110](https://datatracker.ietf.org/doc/html/rfc9110).
  
  While we should be largely up-to-speed, there is at least one known inaccuracy wrt `413 Content Too Large` (see [RFC 9110, Section 15.5.14](https://datatracker.ietf.org/doc/html/rfc9110#name-413-content-too-large)). We still use the older `Payload Too Large`.