Dialogs inheriting from incorrect Component, causing the buttons to be styled incorrectly

CURA-8688

resources/qml/Preferences/MachinesPage.qml

@@ -125,7 +125,7 @@ UM.ManagementPage
             }
         }
 
-        UM.RenameDialog
+        Cura.RenameDialog
         {
             id: renameDialog
             object: base.currentItem && base.currentItem.name ? base.currentItem.name : ""

resources/qml/Preferences/RenameDialog.qml

@@ -11,6 +11,9 @@ import Cura 1.0 as Cura
 UM.Dialog
 {
     id: base
+
+    buttonSpacing: UM.Theme.getSize("default_margin").width
+
     property string object: ""
 
     property alias newName: nameField.text
@@ -64,14 +67,6 @@ UM.Dialog
         }
     }
 
-    Item
-    {
-        ButtonGroup {
-            buttons: [cancelButton, okButton]
-            checkedButton: okButton
-        }
-    }
-
     rightButtons: [
         Cura.SecondaryButton
         {