Change docs around -eo pipefail when shell is not specified

[nikola-jokic]

Why:

Closes #18933

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

Explaining that fail-fast is not applied by default.

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There are multiple issues in the runner repo addressing that the docs are incorrectly stating the behaviour ☺️

[github-actions]

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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
actions/using-workflows/workflow-syntax-for-github-actions.md	fpt ghec ghes@ 3.5 3.4 3.3 3.2 3.1 ghae	fpt ghec ghes@ 3.5 3.4 3.3 3.2 3.1 ghae

[cmwilson21]

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

[martin389]

Thanks for the PR! ✨

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