security: bump minimum tls version for openssl to TLS 1.3

[braindigitalis]

After raising this with Discord they have enabled support for TLS 1.3 on discord.media websocket endpoints. This now allows all of D++ to use TLS 1.3 as a minimum TLS version.

Unit tests now pass with this set.

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[braindigitalis]

This also increases handshake performance significantly. I have not profiled this, but OpenSSL's own docs and third party sites document this handshake change: