Print Go version in rake gitlab:env:info

Why was this MR needed?

Now that Gitaly is a part of GitLab installation, it can be helpful to know Go version in order to debug Gitlay-related bugs.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together