Playground block: open-in-new-tab focus order is visually out-of-sequence

[brandonpayton]

From WordPress/Learn#2783

I thought it would be helpful for the open-in-new-tab link to come first in the focus order for those using assistive technologies, even though we wanted to display the link in the block footer. But it naturally turns out to make visual focus order confusing for keyboard-centric users.