KNOWN_BUGS: Update 11.9 - DoH option inheritance

KNOWN_BUGS: Update 11.9 - DoH option inheritance

- Add description: Explain that some options aren't inherited because
  they are not relevant for the DoH SSL connections or may result in
  unexpected behavior.

- Remove the reference to #4578 (SSL verify options not inherited) since
  that was fixed by #6597 (separate DoH-specific options for verify).

- Explain that DoH-specific options (those created by #6597) are
  available: CURLOPT_DOH_SSL_VERIFYHOST, CURLOPT_DOH_SSL_VERIFYPEER and
  CURLOPT_DOH_SSL_VERIFYSTATUS.

- Add a reference to #6605 and explain that the user's debug function is
  not inherited because it would be unexpected to pass internal handles
  (ie DoH handles) to the user's callback.

Closes https://github.com/curl/curl/issues/6605