docs: made updates about security files and improving sentences

[CBID2]

Why:

This would help users gain a better understanding about the SECURITY.md file and how to effectively use YAML when creating issue forms for their repositories.

Closes #32048

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

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  • 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.

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[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
code-security/getting-started/adding-a-security-policy-to-your-repository.md	fpt ghec ghes@ 3.12 3.11 3.10 3.9	fpt ghec ghes@ 3.12 3.11 3.10 3.9
communities/setting-up-your-project-for-healthy-contributions/creating-a-default-community-health-file.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]

@CBID2 Thanks so much for opening a PR with these fixes! ✨ I made one small adjustment, and removed an unnecessary "on" on line 24 💛

I'll get this merged once tests are passing 🍏

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