mobile: replace undoDelete() with generic undo()

Since we are using the existing command infrastructure, this isn't specific to
undoing a delete.

This commit renames the function and removes its use in the UI, the next commit
will then add the generic undo to the UI.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

mobile-widgets/qml/DiveDetails.qml

@@ -152,14 +152,7 @@ Kirigami.Page {
 		icon {
 			name: ":/icons/trash-empty.svg"
 		}
-		onTriggered: {
-			var deletedId = currentItem.modelData.id
-			manager.deleteDive(deletedId)
-			showPassiveNotification("Dive deleted", 5000, "Undo",
-						function() {
-							manager.undoDelete(deletedId)
-						});
-		}
+		onTriggered: manager.deleteDive(currentItem.modelData.id)
 	}
 
 	property QtObject cancelAction: Kirigami.Action {