Fix sizing of the machine action dialog

Contributes to #7224

resources/qml/Preferences/MachinesPage.qml

@@ -118,7 +118,10 @@ UM.ManagementPage
         UM.Dialog
         {
             id: actionDialog
-
+            minimumWidth: UM.Theme.getSize("modal_window_minimum").width
+            minimumHeight: UM.Theme.getSize("modal_window_minimum").height
+            maximumWidth: minimumWidth * 3
+            maximumHeight: minimumHeight * 3
             rightButtons: Button
             {
                 text: catalog.i18nc("@action:button", "Close")

resources/qml/WelcomePages/WizardDialog.qml

@@ -22,8 +22,8 @@ Window
     flags: Qt.Dialog
     modality: Qt.ApplicationModal
 
-    minimumWidth: 580 * screenScaleFactor
-    minimumHeight: 600 * screenScaleFactor
+    minimumWidth: UM.Theme.getSize("modal_window_minimum").width
+    minimumHeight: UM.Theme.getSize("modal_window_minimum").height
 
     color: UM.Theme.getColor("main_background")