go package management has reference to obsolete repository

[rajcspsg]

The file below references to repository https://github.com/conan-community/conan-goserver-example which is no longer exists.

https://github.com/conan-io/docs/blob/master/howtos/other_languages_package_manager/go.rst

The example needs to be updated.

[SSE4]

adding @uilianries. we recently archived conan-community. btw, I am not sure if we still need these go instructions at all.