Remove language 'go' from README

[gbarnett-hz]

./generator.py -l go doesn't work despite being listed as a language target in README.md.

From what I see the README is incorrect as the golang support looks minimal to non-existant. This PR just remove go from stated set of language targets.

You can generate codecs for a specific language by calling,

./generator.py [-r ROOT_DIRECTORY] [-l LANGUAGE] [-p PROTOCOL_DEFS_PATH] [-o OUTPUT_DIRECTORY] [-n NAMESPACE] [-b BINARY_OUTPUT_DIR] [-t TEST_OUTPUT_DIR] [--no-binary] [--no-id-check]
where

ROOT_DIRECTORY is the root folder for the generated codecs. If left empty, default value is set to ./output/[LANGUAGE].

LANGUAGE is one of

java : Java
cpp : C++
cs : C#
py : Python
ts : TypeScript
go : Go
md : Markdown (Documentation)

./generator.py -l go
usage: generator.py [-h] [-r ROOT_DIRECTORY] [-l LANGUAGE] [-p PROTOCOL_DEFS_PATH] [-o OUTPUT_DIRECTORY] [-n NAMESPACE] [-b BINARY_OUTPUT_DIRECTORY]
                    [-t TEST_OUTPUT_DIRECTORY] [--no-binary] [--no-id-check]
generator.py: error: argument -l/--lang: invalid choice: 'go' (choose from 'java', 'cpp', 'cs', 'py', 'ts', 'md')

Fixes: #471

[ihsandemir]

@yuce ?

[yuce]

Go client support is in this PR: #420
But I don't see it to be merged in the near future, so it's OK to remove go from the README.

[gbarnett-hz]

@yuce + @ihsandemir could you approve this PR then?