fix: uninstallDialog doesn't center in screen

I don't know why it exists when org.deepin.ds.dock is loaded with
the org.deepin.ds.launchpad.
Using layershell to anchor the window's position.

issue: linuxdeepin/developer-center#7824

qml/Main.qml

@@ -325,6 +325,8 @@ QtObject {
         property string appId: ""
         property string appName: ""
 
+        DLayerShellWindow.anchors: DLayerShellWindow.AnchorNone
+
         minimumWidth: layout.implicitWidth + 2 * DS.Style.dialogWindow.contentHMargin
         minimumHeight: layout.implicitHeight + DS.Style.dialogWindow.titleBarHeight
         maximumWidth: minimumWidth