Focus style: Names in credit section

[walbo]

Focus style on names in credit section are broken. See screenshot.

[afercia]

@walbo nice catch. Would be great to take this opportunity to improve the markup too. A nice improvement would be removing redundant links and have just one link that wraps both the image and the name. See ​http://www.w3.org/TR/WCAG20-TECHS/H2.html and discussion on #32254 and #32509.
Basically:

• just one link
• image with an empty alt (no need to repeat the same info that's already in the name)
• style the focus in a similar way to the one on the Media Library attachements

Something like this:

[afercia]

The refreshed patch tries to simplify a bit the markup. There's no need to have two separate links, they can be combined in just one link for better semantics and accessibility as suggested in ​https://www.w3.org/TR/WCAG20-TECHS/H2.html

This would be consistent with what was already done on the Media Library screen, also for the focus style. See screenshot below:

1. currently, both the gravatar and the name are links
2. combined in just one link with the new focus style
3. consistent with the focus style in the Media Library

[walbo]

Added an empty alt attribute to 34953.2.diff. The alt attribute should be left empty and not deleted.

[afercia]

Uops :) thanks @walbo, missed that.

[afercia]

In 36406:

Accessibility: Improve the focus style on the Credits screen.

Leads and contributing developers will now look nicer when focused.
Also, combines adjacent image and text links for the same resource thus
simplifying markup and reducing noise for screen reader users.

Props walbo, afercia.
Fixes #34953.