Remove the "Open file" label from the open file dropdown menu

This will make the translations more reasonable (instead of translating "open file" and "from Disk" separately, which could make the some translation results making less sense.

CURA-8411

plugins/PrepareStage/PrepareMenu.qml

@@ -120,19 +120,6 @@ Item
                         popup.width = childrenRect.width
                     }
 
-                    Label
-                    {
-                        text: catalog.i18nc("@menu:header", "Open file")
-                        color: UM.Theme.getColor("text_medium")
-                        font: UM.Theme.getFont("medium")
-                        renderType: Text.NativeRendering
-                        verticalAlignment: Text.AlignVCenter
-
-                        width: contentWidth
-                        height: UM.Theme.getSize("action_button").height
-                        leftPadding: UM.Theme.getSize("default_margin").width
-                    }
-
                     Repeater
                     {
                         model: prepareMenu.fileProviderModel