Nested list-group-horizontal inside list-group-flush renders without proper borders

Created by: jarodhanko

Bug reports must include:

• Operating system and version (Windows)
• Browser and version (Tested on Chrome and Firefox)
• Test Case : https://codepen.io/jarodhanko/pen/vYEaoKr
• Bootstrap Version: 4.4.1

Perhaps this is a bit of an edge case or simply unsupported behavior, but if you attempt to nest a list-group-horizontal inside of a custom list-group that is using list-group-flush, the list-group-horizontal renders with the inner borders, the side borders, or the top border of the first item. It is inheriting the css from .list-group-flush .list-group-item. Any nested list groups that are not horizontal list groups render as list-group-flush as well.

It works fine with a normal list group.