Supported commands outdated in README

[dspruell]

There are some minor changes in supported rita commands that aren't yet reflected in the README (unsure about other documentation locations). For example:

rita version v4.8.0:

• Supports show-beacons-proxy
• Supports show-beacons-sni
• Supports show-open-connections
• Doesn't support show-dns-fqdn-ips

[dspruell]

I'll propose a PR for this.