Bonsai docs: fix version switcher scheme mismatch (http vs https)

versionURLs in brand.html used http:// while the docs sites are
served over https://, so currentURL.includes(url) never matched and
the <select> never reflected/switched to Unstable. Fixes #8023.

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(cherry picked from commit 780739719f)

src/bonsai/docs/_templates/sidebar/brand.html

@@ -38,8 +38,8 @@ Hope your day's going well. :)
 <script>
   // Define the mapping of versions to URLs
   const versionURLs = {
-    stable: 'http://docs.bonsaibim.org/',
+    stable: 'https://docs.bonsaibim.org/',
-    unstable: 'http://docs-unstable.bonsaibim.org/',
+    unstable: 'https://docs-unstable.bonsaibim.org/',
     // Add more versions here as needed
   };