Plugins: Make the appearance of plugin action links on Add Plugins screen more consistent.

This ensures that the "More Details" link does not randomly wrap to a second line depending on the length of the button label above.

Props sabernhardt, kharisblank, Otto42, paresh07.
Fixes #48648.
Built from https://develop.svn.wordpress.org/trunk@48120


git-svn-id: https://core.svn.wordpress.org/trunk@47889 1a063a9b-81f0-0310-95a4-ce76da25c4cd