Fixed positioning of the sidebar breaks license popover placement

[zackkrida]

Description

The placement of the license popovers is shifted slightly to fit within the bounds of the sidebar now that it is fixed position:

This feels odd—the popover shouldn't care about the filter sidebar's positioning and should be positioned relative to the document, I would think.

Reproduction

1. Run openverse locally on main and submit a search
2. Click any license popover icon in the filter sidebar
3. Observe the odd placement in the screenshot above

[sarayourfriend]

There are some popper.js flags we can manipulate to solve this (I think).

openverse-frontend/src/composables/use-popper.js

Line 34 in 3922733

strategy: 'absolute',

That line might be of particular interest.

[zackkrida]

Thanks @sarayourfriend, yes children of fixed elements need to use the fixed strategy. PR incoming.