[MediaCard] Extraneous space when card has no actions

[kaelig]

Issue summary

In vertical view (smaller viewports), MediaCard without primaryAction or secondaryAction has extra space at the bottom.

Expected behavior (no extraneous space between description and bottom)

Actual behavior (extraneous space between description and bottom)

Reduced test case

      <MediaCard
        title="Turn your side-project into a business"
        description={`In this course, you’ll learn how the Kular family turned their mom’s recipe book into a global business.`}
      >
        <VideoThumbnail
          videoLength={80}
          thumbnailUrl="https://burst.shopifycdn.com/photos/business-woman-smiling-in-office.jpg?width=1850"
        />
      </MediaCard>

https://codesandbox.io/s/determined-flower-1jxxq?file=/App.js

Specifications

• Are you using the React components? (Y/N): Y
• Polaris version number: 7.0.0

[emilycritter]

First time participating in Hacktoberfest and am picking up this issue 🎉