remove all font-size params, let quarto use default

[emaigne]

I removed all the font-size attributes (and padding and spacing), leaving only the font family and color to respect the INRAE graphical chart. It leads to less erratic behaviour in revealjs slides (in my case for lists and sublists as the font-size changed if I added a line break before the item or not). We use this simplify scss to leave quarto use the default, and add specific parameters only when needed

[davidcarayon]

Thanks a lot !