Override column-fill property on popular container at tablet breakpoint. Fixes: #6700

This fixes #6700 turns out both Safari and Firefox were behaving correctly, as the [column-fill](https://developer.mozilla.org/en-US/docs/Web/CSS/column-fill) property defaults to `balance`

This is a temporary fix for US launch until I can submit a PR to guss-layout to enable the author to pass in a column-fill parameter to the column mixin.

/cc @michaelwmcnamara @ironsidevsquincy @sndrs