Fix use of deprecated QML feature in sddm-theme

sddm-theme/Login.qml

@@ -102,7 +102,7 @@ SessionManagementScreen {
 
             Connections {
                 target: sddm
-                onLoginFailed: {
+                function onLoginFailed() {
                     passwordBox.selectAll()
                     passwordBox.forceActiveFocus()
                 }

sddm-theme/Main.qml

@@ -494,13 +494,13 @@ PlasmaCore.ColorScope {
 
     Connections {
         target: sddm
-        onLoginFailed: {
+        function onLoginFailed() {
             notificationMessage = i18nd("plasma_lookandfeel_org.kde.lookandfeel", "Login Failed")
             footer.enabled = true
             mainStack.enabled = true
             userListComponent.userList.opacity = 1
         }
-        onLoginSucceeded: {
+        function onLoginSucceeded() {
             //note SDDM will kill the greeter at some random point after this
             //there is no certainty any transition will finish, it depends on the time it
             //takes to complete the init