Quiet radio keyboard focus uses the wrong color

[LFDanLu]

Blocked by outstanding design question. We will bring this up in workshop.

Description

Fixes https://github.com/adobe/spectrum-css/issues/736

Stops focus from overriding the selected radio button border color. This brings it in line with design. Lemme know if this shouldn't be done, noted this when adding the halo focus rings to v3 RSP.

Design XD file screenshot

How and where has this been tested?

Tested by building locally and navigating to http://localhost:3002/docs/radio.html. Tabbed to each of the radio buttons to make sure their original color wasn't overwritten by keyboard focus

Did this in Chrome 81, Firefox 75, Safari 13.1 in MacOS 10.15

Screenshots

Before:

After:

To-do list

• [x] If my change impacts other components, I have tested to make sure they don't break.
• [x] If my change impacts documentation, I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.

• [x] This pull request is ready to merge.

[GarthDB]

@LFDanLu this seems accurate, but I want to double-check we are using the DNA vars fully.

[pfulton]

Radio has changed dramatically since this PR was submitted. Closing for now, but am happy to reopen later if necessary.