Add GHES 3.7 Performance Numbers

[susanzhang27]

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 should be now reflected for 3.7. GHES 3.7 numbers are the same as 3.6.

Additional information

No response

[welcome[bot]]

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[cmwilson21]

👋 @susanzhang27 - Thanks for opening an issue and linking it to your PR! ✨