gRPC version prompt

[michaelchao]

I'm now using otel-cpp with gRPC, however compile failed, I don't now what version of gRPC should I use. SI I recommend adding version required infomation for gRPC in README.

[owent]

We support many versions of gRPC, which one to use depends on your build system.
If you do not use gRPC before, here is a recommend versions of depended packages: https://github.com/open-telemetry/opentelemetry-cpp/blob/main/third_party_release

[marcalff]

As @owent described:

• opentelemetry-cpp does not require a specific version of grpc. Instead, the model is that opentelemetry-cpp uses the version of grpc that might be already used by the application, due to other dependencies.
• If there are no reasons to use a specific version, a good choice is to pick the version used in CI tests. Currently, this is gRPC=v1.49.2, per the third_party_release file.

Accepting this report as a documentation issue, so that the README or related doc mention clearly where to find the current information for each dependency.

[michaelchao]

Tks all suggestions

[michaelchao]

Ths, done