grpc-usage-example is outdated

[bzz]

https://docs.sourced.tech/babelfish/using-babelfish/grpc-usage-example is not relevant to v2 of the protocol.

It should be either

• re-wroked, to include details how gRCP + libuast work together for decoding and filtering or
• removed completely

From the discussion at LA Focus week consensus seem to be - as we do not want to expose it to end users, it might be either removed or moved to developer documentation.

Waiting for triage \cc @src-d/language-analysis