BUG: Fix JSON typo that breaks javascript in the docs
Closes #61571 

As opposed to Python, JSON doesn't accept commas after the last element of a dict, and it's strict about it. We added this as a typo (I think I did the same during a release, I'll create an issue to validate this JSON in the CI) when updating the JSON that provides the versions for the documentation drop down. This seems to be breaking all the javascript in our docs.

@mroeschke I would merge this before waiting for the CI, but up to you.
Is this failure related? https://github.com/pandas-dev/pandas/actions/runs/15474985199/job/43567905639?pr=61572

```bash
Writing evaluated template result to /home/runner/work/pandas/pandas/doc/build/html/_static/nbsphinx-code-cells.css

Extension error (pydata_sphinx_theme):
Handler <function update_config at 0x7f4fee50fbe0> for event 'builder-inited' threw an exception (exception: Expecting property name enclosed in double quotes: line 17 column 5 (char 392))
``` I'm pretty sure it's not, but no idea where this exception is coming from, I'm having a look now and see if I can understand what's going on. I'll rerun the job Ok, I think it's kind of related, but I think this is failing because it's fetching the `versions.json` published online, which has the typo. I checked this is also broken in `main` (locally), so I'm going to merge, and hopefully we don't see this CI error anymore. The CI after merging also failed, since building the website fetches the file in production (kind of nonsense, but that's how the sphinx theme works), so we were in a loop where we can't fix the website because production is broken, and we can't update production because the website is broken. I updated the file in the server directly, and now everything should be fine. The dropdown works for me already, but the file with the typo may be cached for others I guess.