Replace non-breaking spaces with normal spaces

[aisk]

When reading the documents, I found that a Markdown marker was not rendered correctly by GitHub. I discovered that this was caused by a non-breaking space (\xa0):

There are some more non-breaking spaces in the codebase, so I just changed them as well.

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📚 Documentation preview 📚: https://cpython-previews--130116.org.readthedocs.build/

[mhsmith]

Most of these probably happened by accidentally pressing option+space on macOS, or similar things on other platforms.

[freakboy3742]

These changes all make sense to me (in that that they seem to be no-ops and almost certainly accidental typos); my only cause for concern are the changes to historical change notes. I don't think that's a problem, but I'm not 100% sure. I'll confirm with docs maintainers.

[freakboy3742]

I've confirmed there's no issue with updating historical release notes, so this is good to merge. I'll also mark it for backport to 3.13. Thanks for the PR!

[miss-islington-app]

Thanks @aisk for the PR, and @freakboy3742 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.12, 3.13.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @aisk and @freakboy3742, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 798f8d3ea9f54ee80a684bff74f67ee7d99e35c2 3.13

[miss-islington-app]

Sorry, @aisk and @freakboy3742, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 798f8d3ea9f54ee80a684bff74f67ee7d99e35c2 3.12

[freakboy3742]

Looks like the backport isn't trivial; since it isn't essential these fixes are backported, I'll leave them as main-only.

[terryjreedy]

Try to remember to remove backport labels when deciding not needed ;-)