gh-38274: Fix broken anchors in CHANGES.html of doc preview
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broken by careless code in #38213:
```
# Restore the new doc from changes by "wipe out"
(cd docs && git checkout -f)
```
which also wipes out anchors planted by `.ci/create-changes-html.sh`!
To reviewer: changes over #38220 is in https://github.com/sagemath/sage/
pull/38274/commits/d2d1514148f46a4ceeea650eab1fd0a0800ebbc9
Tested in :
https://github.com/kwankyu/sage/actions/runs/9659812609/job/26643993813.
Try to open https://doc-pr-43--sagemath-
test.netlify.app/html/en/reference/references/#hunk2 to check
### :memo: Checklist
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- [ ] I have updated the documentation and checked the documentation
preview.
### :hourglass: Dependencies
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#38220
URL: https://github.com/sagemath/sage/pull/38274
Reported by: Kwankyu Lee
Reviewer(s):
