sagemathgh-37689: Fix changes.html in doc preview

    
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by changing the base doc url.

The base doc url is where the doc preview for the released version is
uploaded. It changed recently:
sagemath#34874 (comment),
but we didn't fix accordingly here: [.ci/create-changes-
html.sh](https://github.com/sagemath/sage/blob/develop/.ci/create-
changes-html.sh)

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- [ ] I have updated the documentation accordingly.

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URL: sagemath#37689
Reported by: Kwankyu Lee
Reviewer(s):

.ci/create-changes-html.sh

@@ -19,8 +19,8 @@ echo '<script>hljs.highlightAll();</script>' >> CHANGES.html
 cat >> CHANGES.html << EOF
 <script>
 document.addEventListener('DOMContentLoaded', () => {
+const baseDocURL = 'https://sagemath.netlify.app'
 const diffSite = 'https://pianomister.github.io/diffsite'
-const baseDocURL = 'https://sagemath-tobias.netlify.app'
 const diffParagraphs = document.querySelectorAll('p.diff');
 diffParagraphs.forEach(paragraph => {
   const rootURL = window.location.origin;