[Documentation] Google Protobuf Implementation

[CSSFrancis]

For older versions of python Google protobuf might not work properly. The way to get it to work is to fall back on to the python implementation. by setting the environmental variable.

export PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION = python

See https://github.com/protocolbuffers/protobuf/blob/main/python/README.md#implementation-backends for more information.