Accessibility: Remove title attributes from the updates links on the Plugin and Themes list tables.

Adds `aria-label` attributes on some links and on the "update nag" link. Adds translator comments.

Fixes #35167.
Built from https://develop.svn.wordpress.org/trunk@36032


git-svn-id: https://core.svn.wordpress.org/trunk@35997 1a063a9b-81f0-0310-95a4-ce76da25c4cd