GitLab-Shell used to implement the Git hooks that performed
authorization and authentication. These were ported to Go, and since
61dcdf969231954c06f16a6222a7540460f4b4f0 these are merged, meaning that
the code this change removes isn't ever called. As such, we should
remove it.
Removing these files required updates to the Makefile as some make
targets are no longer needed as the gitlab-shell tests aren't executed
anymore.