Update docs for generating a new SSH key for windows

[williamtorres1]

I was trying to add a ssh key to my github using windows 10, and i was uncapable to procceed.
And i found that the commands $ eval $(ssh-agent -s) don't work on windows, but $ evalssh-agent -s works fine

Why:

What's being changed:

Check off the following:

• All of the tests are passing.
• I have reviewed my changes in staging. (look for the deploy-to-heroku link in your pull request, then click View deployment)
• For content changes, I have reviewed the localization checklist
• For content changes, I have reviewed the Content style guide for GitHub Docs.

[welcome]

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

[janiceilene]

@williamtorres1 Thanks so much for opening a PR! I'll get this triaged for review ⚡

[shati-patel]

I can confirm this works on Windows ✔️

Thank you very much for your contribution @williamtorres1, I'll get this merged once the tests pass 🎉

[Simran-B]

In what windows shell does this work?

[shati-patel]

In what windows shell does this work?

It should work in a Git Bash shell for Windows 🙂

In fact, both the $ eval $(ssh-agent -s) and $ eval `ssh-agent -s` syntax work in my version, but the latter seems more universal (according to various comments on stackoverflow 😅).

[shati-patel]

I'm going to quickly close and re-open this PR to (hopefully) kick-start the staging deployment and get the PR checks green 🤞🏽

[Simran-B]

Thanks for the clarification! I missed that the instructions say "Open Git Bash" earlier. I would prefer a true Windows solution that doesn't require an emulated Linux, but this is still a meaningful change.

[github-actions]

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