Add GHES 3.6 Performance Numbers

[bquantump]

Code of Conduct

• [X] I have read and agree to the GitHub Docs project's Code of Conduct

What article on docs.github.com is affected?

getting-started-with-github-actions-for-github-enterprise-server.md

What part(s) of the article would you like to see updated?

The performance numbers matrix for vCPU to connected runners. Also note the new definition of connected runners

Additional information

No response

[welcome[bot]]

Thanks for opening this issue. A GitHub docs team member should be by to give feedback soon. In the meantime, please check out the contributing guidelines.