[Login, Lock, and Logout Screen] Make the avatar background circle more subtle
Summary: Added in D16879, the background circle was designed to work on a blurless login screen. Since we have abandoned that idea, it's good to adjust it to our present needs. This patch lowers the opacity of the circle and removes the double border it created.
Reviewed By: ngraham, VDG, rooty
Subscribers: abetts, plasma-devel
Maniphest Tasks: T10325
Differential Revision: https://phabricator.kde.org/D19478