doc: remove unused error codes from errors.md

This removes two unused error codes:
 * ERR_STREAM_READ_NOT_IMPLEMENTED, removed in c9794880 (PR #18813).
 * ERR_VALUE_OUT_OF_RANGE, removed in d022cb1b (PR #17648).

PR-URL: https://github.com/nodejs/node/pull/21491


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>