🐛 [BUG] - Card component has incorrectly-sized border in dark colour mode

[joshfarrant]

Describe the bug

In the "dark" colour mode, the border of the Card component doesn't take up the full size of the component.

I think this is a regression caused by #746.

Reproduction steps

View the Border example in the Card docs in dark color mode.

Or, render the following component within a ThemeProvider with colorMode="dark"

<Card href="https://github.com" hasBorder>
  <Card.Heading>Code search & code view</Card.Heading>
  <Card.Label>Limited</Card.Label>
  <Card.Description>
    Enables you to rapidly search, navigate, and understand code, right from
    GitHub.com.
  </Card.Description>
</Card>

Expected behavior

The border goes around the edge of the Card component.

Screenshots

Browsers

Chrome

OS

Mac