gh-90437: Fix __main__.py documentation wording

[tavallaie]

Complete fix for Issue #90437 with cherry-picked commits from @riqts and @merwok

This commit builds upon the previous work done by @riqts to address Issue #90437. It includes cherry-picked commits from their branch, ensuring their contributions are recognized and preserved in the project's history.

Cherry-picked commits:

• Commit 1: Fixed simple __main__ typo (c30b653)
• Commit 2: those files are kept short, importing functions to execute from other modules (0611a6c)

Special thanks to @riqts and @merwok for their initial contributions to this issue.

Ali Tavallaie

• Issue: gh-90437

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📚 Documentation preview 📚: https://cpython-previews--116309.org.readthedocs.build/

[tavallaie]

I'll keep it updated until it merged

[miss-islington-app[bot]]

Thanks @tavallaie for the PR, and @brettcannon for merging it 🌮🎉.. I'm working now to backport this PR to: 3.12, 3.13. 🐍🍒⛏🤖

[bedevere-app[bot]]

GH-121385 is a backport of this pull request to the 3.13 branch.

[bedevere-app[bot]]

GH-121386 is a backport of this pull request to the 3.12 branch.