Fix version switcher issues on GH docs page

[shaahji]

Fix version switcher issues on GH docs page

Root cause: versions.json was modified on release branch and the automation script even updated the local versions file to add the new version, however, the build configuration wasn't using the local file. The build was configured to use the file from last released version on GH.

Checklist before requesting a review

• Add unit tests for this change.
• Make sure all tests can pass.
• Update documents if necessary.
• Lint and apply fixes to your code by running lintrunner -a
• Is this a user-facing change? If yes, give a description of this change to be included in the release notes.

(Optional) Issue link

[Copilot]

Pull request overview

Fixes the Sphinx docs version switcher on GitHub Pages by ensuring it uses the versions list that is shipped with the docs being built, instead of fetching a potentially stale versions file from the currently deployed site.

Changes:

• Update pydata_sphinx_theme switcher configuration to load versions.json from the local _static directory.
• Refresh docs/source/_static/versions.json to mark 0.12.1 as latest and add 0.12.0.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
docs/source/conf.py	Points the theme’s version switcher at the locally built _static/versions.json so the build uses the updated list.
docs/source/_static/versions.json	Updates the published version entries and latest designation for the docs switcher.