Updated the environment-variables.md

[Sreelayavuyyuru]

Why:

Closes #2693

What's being changed:

I have followed the instructions in the issue to fix this. I have corrected the text in the note box to the mentioned paragraph.
That is,
"When you set a custom environment variable, you cannot use any of the default environment variable names listed above with the prefix GITHUB_. If you attempt to override the value of one of these default environment variables, the assignment is ignored."

I did not remove the Note: (After reviewing the localization checklist) because it was mentioned that the previous one should be change to 'rather a note'.

I am just getting started with open-source so I am sorry if I have done anything that is incorrect.

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.

[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.

[ajsirota]

Looks great to me! 👍

[janiceilene]

👋 @Sreelayavuyyuru Thank you so much for opening a PR with this fix!

in content/actions/reference/environment-variables.md, change... to a simple paragraph (rather than a note)

From that statement in the issue, I think we do want to remove the {% note %} and {% endnote %} tags. Since this file is a reusable, it's visible in a few different articles and it looks like @hubwriter would prefer it show up in the article as a paragraph, instead of a note.

Let me know when you've removed the tags and I'll get this up for review ⚡

[Sreelayavuyyuru]

Hey @janiceilene, Thank you so much for the instructions!
I have removed the tags, so it looks like a paragraph now like you mentioned 👍🏼

[lecoursen]

Thanks for fixing this! I'll merge it now.

[github-actions]

Thanks very much for contributing! Your pull request has been merged 🎉 You should see your changes appear on the site in approximately 24 hours. If you're looking for your next contribution, check out our help wanted issues ⚡