gh-148552: Document the loop argument in ensure_future() method

[manoj-km24]

Document loop argument in Doc/library/asyncio-future.rst under the ensure_future() method.

• Issue: Document loop argument in ensure_future method #148552

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📚 Documentation preview 📚: https://cpython-previews--148553.org.readthedocs.build/

[picnixz]

I do not think it is necessary to document it only in one function. Just document it at the toplevel of the module somehow brcause it is not the only function taking n optionsal loop.

[bedevere-app]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[manoj-km24]

I have made the requested changes; please review again.

[bedevere-app]

Thanks for making the requested changes!

@picnixz: please review the changes made to this pull request.

[manoj-km24]

I can relocate the paragraph somewhere else if you have a better suggestion