[Notifications] Fix grouping container side line

Base the width on the actual thickness of the SVG provided by the theme,
otherwise it might get stretched way too much.


(cherry picked from commit 31b3a130)

applets/notifications/package/contents/ui/FullRepresentation.qml

@@ -414,7 +414,8 @@ PlasmaComponents3.Page {
                                             elementId: "vertical-line"
                                             svg: lineSvg
                                             anchors.horizontalCenter: parent.horizontalCenter
-                                            width: PlasmaCore.Units.iconSizes.small
+                                            // Want a thicker than default bar
+                                            width: Math.min(groupLineContainer.width, naturalSize.width * PlasmaCore.Units.devicePixelRatio * 3)
                                             height: parent.height
                                         }
                                     }