[applets/kickoff] Re-add Avatar to the focus chain

Need to make sure it can take focus too.

(cherry picked from commit d7910423)

applets/kickoff/package/contents/ui/Header.qml

@@ -81,6 +81,9 @@ PlasmaExtras.PlasmoidHeading {
 
         Kirigami.Avatar {
             id: avatarButton
+
+            activeFocusOnTab: true
+
             source: kuser.faceIconUrl
             name: nameLabel.text