Disable support for SSL 3 protocol

Not sure if this'll work, but I believe it will disable negotiation for both the SSL 2 and SSL 3 protocols, leaving it to be TLS 1, 1.1, 1.2, or future versions yet to be written.

__Justification:__
* [A Public Statement Regarding Ubiquitous Encryption on the XMPP Network](https://github.com/stpeter/manifesto/blob/master/manifesto.txt)
* [Use of Transport Layer Security (TLS) in the Extensible Messaging and Presence Protocol (XMPP)](https://datatracker.ietf.org/doc/draft-saintandre-xmpp-tls/)