Added instruction for ignoring the Gemfile.lock file to prevent unsatisfiable dependencies warning in the creating-a-github-pages-site-with-jekyll page

[revolter]

Why: Warning prevention

Closes: #32351

What's being changed (if available, include any code snippets, screenshots, or gifs):

• The existing instructions implicitly make you commit and push the Gemfile.lock file, and this PR fixes this

Check off the following:

• I have reviewed my changes in staging, available via the View deployment link in this PR's timeline (this link will be available after opening the PR).

  • For content changes, you will also see an automatically generated comment with links directly to pages you've modified. The comment won't appear if your PR only edits files in the data directory.

• For content changes, I have completed the self-review checklist.

[github-actions]

Automatically generated comment ℹ️

This comment is automatically generated and will be overwritten every time changes are committed to this branch.

The table contains an overview of files in the content directory that have been changed in this pull request. It's provided to make it easy to review your changes on the staging site. Please note that changes to the data directory will not show up in this table.

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Content directory changes

You may find it useful to copy this table into the pull request summary. There you can edit it to share links to important articles or changes and to give a high-level overview of how the changes in your pull request support the overall goals of the pull request.

Source	Preview	Production	What Changed
pages/setting-up-a-github-pages-site-with-jekyll/creating-a-github-pages-site-with-jekyll.md	fpt ghec ghes@ 3.12 3.11 3.10 3.9	fpt ghec ghes@ 3.12 3.11 3.10 3.9

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fpt: Free, Pro, Team
ghec: GitHub Enterprise Cloud
ghes: GitHub Enterprise Server

[nguyenalex836]

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

[revolter]

npm ERR! code E401
npm ERR! 401 Unauthorized - GET https://npm.pkg.github.com/@github%2fcocofix - authentication token not provided
npm ERR! A complete log of this run can be found in: /home/runner/.npm/_logs/2024-04-03T06_24_50_430Z-debug-0.log
Error: Process completed with exit code 1.

I think that the failing lint job is not actually caused by this PR.