DOC: Use container directives instead of raw html for the doc "cards"
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

The PR is a follow up of #31156 and #31148 translating the raw html to docutils/sphinx directives, making it more _readable_. 

Furthermore, it fixes the redundant css in `pandas.css` versus `getting_started.css` by removing the `install-card` class and merging it with the existing `intro-card` class. 

__Note:__ The setup required an [adjustment to the theme](https://github.com/pandas-dev/pydata-bootstrap-sphinx-theme/pull/92) to overcome the usage of the `container` class by both docutils and bootstrap. 