…ge on 8-col layout

- Adds a 1rem gap between the .p-rule--muted footer divider and the
  card border/image for the 8-column content card variant on large
  screens (>= breakpoint-large), so the rule no longer touches the
  edges.
- Removes dead/redundant CSS from the image-top 8-col override
  (inert grid-column/grid-row resets and a duplicate width: 100%)
  since the parent switches to display: flex at that breakpoint.

Co-authored-by: Oni Benjamin <onibenjo@gmail.com>

…nilla-framework

Fix spacing between muted rule and border/image on 8-col content card