Update define-metadata.rst

[Juke34]

update Skipping builds paragraph to clarify the use. I would like to improve the Skipping builds paragraph to give a better view of its use. I'm unsure about the list of term accepted within the square brackets, did I forget unix ? Do other terms are accepted?

[anaconda-issue-bot]

We require contributors to sign our Contributor License Agreement, and we don't have one on file for @Juke34. In order for us to review and merge your code, please e-sign the PDF at https://conda.io/en/latest/contributing.html#conda-contributor-license-agreement. We then need to manually verify your signature. We will ping the bot to refresh the PR status when we have confirmed your signature.

[github-actions[bot]]

Hi there, thank you for your contribution!

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed automatically if no further activity occurs.

If you would like this pull request to remain open please:

1. Rebase and verify the changes still work
2. Leave a comment with the current status

NOTE: If this pull request was closed prematurely, please leave a comment.

Thanks!

[github-actions[bot]]

Hi there, thank you for your contribution!

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed automatically if no further activity occurs.

If you would like this pull request to remain open please:

1. Rebase and verify the changes still work
2. Leave a comment with the current status

NOTE: If this pull request was closed prematurely, please leave a comment.

Thanks!