Update instructions

[exquo]

Thanks!

Yes, the libsignal-client format has changed recently.

I have made some small changes:

• Since it's now just a single file that needs patching, I've placed the version numbers right into the command string.
  • Probably no need to draw special attention to the absence of v in version numbers here.
• For "The specific libsignal-client version required" it's better to use https://github.com/AsamK/signal-cli/wiki/Provide-native-lib-for-libsignal#determine-the-required-libsignal-client-version which is part of the instructions linked above in this readme.

Let me know if you have any comments!

[orazioedoardo]

Approved.