deps,doc: move openssl maintenance guide to doc

The maintainenance guides are mostly in doc/guides-maintaining-*.md, so
move the OpenSSL one there, too.

PR-URL: https://github.com/nodejs/node/pull/32209


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>