protocol.rst: state version of protocol explained
protocol.rst: state version of protocol explained

If anyone were to understand how to use the server.version method, they would need to know the exact version of the protocol they are using, and to know that, the documentation should explicitly state it, itself.

Last change of the announced version of the protocol in electrum is 0.10:
https://github.com/spesmilo/electrum/commit/118052d81597eff3eb636d242eacdd0437dabdd6
spesmilo/electrum-docs