CI/DOC: pin pydata-sphinx-theme to 0.8.0
Temporary fix for https://github.com/pandas-dev/pandas/issues/46615
Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

```
git checkout 1.4.x
git pull
```

2. Cherry pick the first parent branch of the this PR on top of the older branch:
```
git cherry-pick -x -m1 cd1ab27f9289613ae851e540a842600bcce4bb98
```

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

```
git commit -am 'Backport PR #46663: CI/DOC: pin pydata-sphinx-theme to 0.8.0'
```

4. Push to a named branch:

```
git push YOURFORK 1.4.x:auto-backport-of-pr-46663-on-1.4.x
```

5. Create a PR against branch 1.4.x, I would have named this PR:

> "Backport PR #46663 on branch 1.4.x (CI/DOC: pin pydata-sphinx-theme to 0.8.0)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the `Still Needs Manual Backport` label once the PR gets merged.

If these instructions are inaccurate, feel free to [suggest an improvement](https://github.com/MeeseeksBox/MeeseeksDev).
                 Thanks @jorisvandenbossche I'll do the manual backport for now so that we don't have the issue on 1.4.3

(since I keep the doc build container around just in case and did the version change manually and rebuilt the docs rather than updating the release scripts)