The docs are all being migrated over to Confluence from the old wiki. Any time you see a link to something on wiki.freeswitch.org you should definitely check the Confluence page first. In a pinch just click the "Docs" link on freeswitch.org.
That all being said, there does not seem to be an equivalent page in Confluence. However, if you search for "sip_secure_media" in Confluence you'll see several links that mention the change to "rtp_secure_media" and other helpful information.