Alternatively allow backspace to delete selection

I thought we already had this?

Fixes #6475.

resources/qml/Actions.qml

@@ -258,7 +258,7 @@ Item
         text: catalog.i18ncp("@action:inmenu menubar:edit", "Delete Selected Model", "Delete Selected Models", UM.Selection.selectionCount);
         enabled: UM.Controller.toolsEnabled && UM.Selection.hasSelection;
         iconName: "edit-delete";
-        shortcut: StandardKey.Delete;
+        shortcut: StandardKey.Delete | "Backspace"
         onTriggered: CuraActions.deleteSelection();
     }