Change modals for large screens from 10% position from top and 80% max
height, to 5% position from top and 90% max height.
This is to accommodate the taller cookies policy modal.
It seems that it is not easy to apply a custom position and height to a
specific modal only. This doesn't seem to be supported by the modal
library currently being used.
Before the recent changes, most modals were rendering at 10px top
position (not the originally planned 10%), so changing this to 5%
doesn't seem to be much of a compromise.
When there is enough content in the modal, the height of the modal plus
its top margin could exceed the height of the viewport.
Considering a top position of 10%, a max height of 80% renders a tall
modal vertically centered, with 10% remaining space at the bottom.
