Make the height of the stage buttons themable. Now the height has to be

28px as indicated by the UXers.

Contributes to CURA-5784.

resources/qml/MainWindow/MainWindowHeader.qml

@@ -60,7 +60,7 @@ Rectangle
                 anchors.verticalCenter: parent.verticalCenter
                 exclusiveGroup: mainWindowHeaderMenuGroup
                 style: UM.Theme.styles.main_window_header_tab
-                height: Math.round(0.56 * UM.Theme.getSize("main_window_header").height)
+                height: UM.Theme.getSize("main_window_header_button").height
                 onClicked: UM.Controller.setActiveStage(model.id)
                 iconSource: model.stage.iconSource
 

resources/themes/cura-light/theme.json

@@ -361,7 +361,7 @@
         "window_minimum_size": [106, 66],
 
         "main_window_header": [0.0, 4.5],
-        "main_window_header_button": [8, 4],
+        "main_window_header_button": [8, 2.35],
         "main_window_header_button_icon": [1.2, 1.2],
 
         "stage_menu": [0.0, 4.5],