widgets/wrapper: set WrapperRectangle border.width to 0

Works around the implicit 1px border applied to Rectangles
when border is accessed, and works around QTBUG-137166.

src/ui/ReloadPopup.qml

@@ -118,6 +118,7 @@ PanelWindow {
 		anchors.fill: parent
 		color: palette.active.window
 		border.color: root.failed ? "#b53030" : palette.active.accent
+		border.width: 1
 
 		radius: 10
 		margin: 10

src/widgets/WrapperRectangle.qml

@@ -58,6 +58,12 @@ Rectangle {
 	/// See @@WrapperManager.child for details.
 	property alias child: manager.child
 
+	// Reading the border property implicitly sets border width to 1.
+	// Setting it to 0 here means the user will also have to set border.width
+	// even if they just want 1, but it prevents adding unexpected padding
+	// and works around QTBUG-137166 otherwise.
+	border.width: 0
+
 	MarginWrapperManager {
 		id: manager
 		extraMargin: (root.contentInsideBorder ? root.border.width : 0) + root.extraMargin