Update getting_started.css
The problem is "DOC: Intro to pandas table not readily visible in dark mode #60024"
Perhaps we could set this part of the font color to blue, which is highly visible in either bright or dark mode, so that there is no need to implement a font color that changes with the theme.
So I made a very simple change in the documentation by setting the font color in .tutorial-card-header-2 to blue so that the font can be seen in either bright or dark mode.
> It seems preferable to me to agree with other versions of this page. Both `dev` and `2.1` display correctly, it's just 2.2 that does not. Why is this? Could it be a regression in the pydata-sphinx-theme that has since been fixed?

I noticed that both Dev and 2.2 are built with PyData-Sphinx-theme 0.14.4, so maybe something else is wrong. 
The issue raised on the PyData-Sphinx-theme's github didn't have anyone raise the same issue as the pandas 2.2 version, so maybe we can wait until the new version is released and see what happens.