Add note on 1K limit for GitHub Actions token

[nschonni]

Why:

Using the built-in token only provides 1K requests vs. a user PAT as currently documented.

What's being changed:

Adding small note to existing rate limit doc, that should probably be word-smithed by someone from the product team.

Check off the following:

• 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.

[janiceilene]

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

[skedwards88]

Thank you for opening this PR to clarify the docs! Can you point me to where you found this rate limit?

[nschonni]

https://github.com/tabatkins/bikeshed/runs/2007469198?check_suite_focus=true#step:5:11
Maybe its unique to the GITHUB_TOKEN running as part of a cron job, but I didn't try other combos

[skedwards88]

Thank you for opening this issue! I confirmed your finding with the engineering team:

GITHUB_TOKEN is limited to 1000 requests per hour per repository. For organizations that belong to a GitHub Enterprise Cloud account, this limit is 15,000 requests per hour per repository.

I updated your PR with this info. Thank you again for your contribution! 💖 I'll get this merged down for you.

[nschonni]

I think the 15K part is covered a few lines above (in the conditional rendering), but happy for you to word-smith as much as you like