Is your feature request related to a problem? Please describe...

When using Card Integrated Tabs, the active tab background defaults to $body-bg.

Describe the solution you'd like

The active tab background should default to $card-bg rather than $body-bg, to match the background of the card.

Describe alternatives you've considered

It can easily be overridden with scss, e.g.

.card-header-tabs .nav-link.active {
  background: $card-bg;
  border-color: $card-border-color $card-border-color $card-bg;
}

but I believe it makes sense to not have to go down that road.

Additional context